Now that Aaron is back, I think its about time to start updateing the Essentials. I've compiled a list of cards from Alara Block, M10, Zendikar, and Worldwake that could be playable in the Essentials. And I beleive that the Essentials needs to be updated to the new 5-color rules too.

Shards of Alara
http://findmagiccards.com/Cards/SA/Bant_Panorama.html
http://findmagiccards.com/Cards/SA/Esper_Panorama.html
http://findmagiccards.com/Cards/SA/Grixis_Panorama.html
http://findmagiccards.com/Cards/SA/Jund_Panorama.html
http://findmagiccards.com/Cards/SA/Naya_Panorama.html
Blightning (it is damn good... I'm not using it though...): http://findmagiccards.com/Cards/SA/Blightning.html
Oblivion Ring (already included for Lorwyn, right?): http://findmagiccards.com/Cards/SA/Oblivion_Ring.html
Druid of the Anima (fixes two colors, but not better than Skyshroud Elf I'd say): http://findmagiccards.com/Cards/SA/D...the_Anima.html
Wild Nacatl: http://findmagiccards.com/Cards/SA/Wild_Nacatl.html
Hissing Iguanar (this can get kind of silly in multiplayer): http://findmagiccards.com/Cards/SA/Hissing_Iguanar.html
Relic of Progenitus (some of the best GY hate printed): http://findmagiccards.com/Cards/SA/R...rogenitus.html
Arcane Sanctum: http://findmagiccards.com/Cards/SA/Arcane_Sanctum.html
Crumbling Necropolis: http://findmagiccards.com/Cards/SA/C...ecropolis.html
Jungle Shrine: http://findmagiccards.com/Cards/SA/Jungle_Shrine.html
Savage Lands: http://findmagiccards.com/Cards/SA/Savage_Lands.html
Seaside Citadel: http://findmagiccards.com/Cards/SA/Seaside_Citadel.html
http://findmagiccards.com/Cards/SA/Bant_Charm.html
http://findmagiccards.com/Cards/SA/Esper_Charm.html
http://findmagiccards.com/Cards/SA/Grixis_Charm.html
http://findmagiccards.com/Cards/SA/Jund_Charm.html
Rhox War Monk: http://findmagiccards.com/Cards/SA/Rhox_War_Monk.html
Sprouting Thrinax: http://findmagiccards.com/Cards/SA/S...g_Thrinax.html
Tidehollow Sculler: http://findmagiccards.com/Cards/SA/T...w_Sculler.html
Woolly Thoctar: http://findmagiccards.com/Cards/SA/Woolly_Thoctar.html
Corpse Connoisseur: http://findmagiccards.com/Cards/SA/C...nnoisseur.html
Broodmate Dragon: http://findmagiccards.com/Cards/SA/B...te_Dragon.html
Cruel Ultimatum: http://findmagiccards.com/Cards/SA/Cruel_Ultimatum.html
Stoic Angel: http://findmagiccards.com/Cards/SA/Stoic_Angel.html
Invincible Hymn (I refuse to play it, but it is good): http://findmagiccards.com/Cards/SA/Invincible_Hymn.html
Knight of the White Orchid: http://findmagiccards.com/Cards/SA/K...te_Orchid.html
Ranger of Eos: http://findmagiccards.com/Cards/SA/Ranger_of_Eos.html
Flameblast Dragon: http://findmagiccards.com/Cards/SA/F...st_Dragon.html
Ajani Vengeant: http://findmagiccards.com/Cards/SA/Ajani_Vengeant.html
Elspeth, Knight-Errant: http://findmagiccards.com/Cards/SA/E...ht_Errant.html
Empyrial Archangel: http://findmagiccards.com/Cards/SA/E...Archangel.html
Hellkite Overlord: http://findmagiccards.com/Cards/SA/H..._Overlord.html
Prince of Thralls: http://findmagiccards.com/Cards/SA/P...f_Thralls.html
Rafiq of the Many: http://findmagiccards.com/Cards/SA/R..._the_Many.html
Sarkhan Vol: http://findmagiccards.com/Cards/SA/Sarkhan_Vol.html
Sharuum the Hegemon: http://findmagiccards.com/Cards/SA/S...e_Hegemon.html
Tezzeret the Seeker: http://findmagiccards.com/Cards/SA/T...he_Seeker.html

Conflux
Rupture Spire: http://findmagiccards.com/Cards/CF/Rupture_Spire.html
Armillary Sphere: http://findmagiccards.com/Cards/CF/A...ry_Sphere.html
Reliquary Tower (some people really like this): http://findmagiccards.com/Cards/CF/Reliquary_Tower.html
Path to Exile: http://findmagiccards.com/Cards/CF/Path_to_Exile.html
Shard Convergence: http://findmagiccards.com/Cards/CF/S...nvergence.html
Exotic Orchard: http://findmagiccards.com/Cards/CF/Exotic_Orchard.html
Inkwell Leviathan: http://findmagiccards.com/Cards/CF/I...Leviathan.html
Knight of the Reliquary: http://findmagiccards.com/Cards/CF/K...Reliquary.html
Magister Sphinx (at least in the wishboard): http://findmagiccards.com/Cards/CF/Magister_Sphinx.html
Martial Coup: http://findmagiccards.com/Cards/CF/Martial_Coup.html
Meglonoth: http://findmagiccards.com/Cards/CF/Meglonoth.html
Noble Hierarch: http://findmagiccards.com/Cards/CF/Noble_Hierarch.html
Obelisk of Alara: http://findmagiccards.com/Cards/CF/O..._of_Alara.html
Scepter of Fugue: http://findmagiccards.com/Cards/CF/S..._of_Fugue.html
Wall of Reverence: http://findmagiccards.com/Cards/CF/W...Reverence.html
Conflux: http://findmagiccards.com/Cards/CF/Conflux.html
Maelstrom Archangel: http://findmagiccards.com/Cards/CF/M...Archangel.html
Nicol Bolas, Planeswalker: http://findmagiccards.com/Cards/CF/N...neswalker.html
Progenitus: http://findmagiccards.com/Cards/CF/Progenitus.html
Thornling: http://findmagiccards.com/Cards/CF/Thornling.html

Alara Reborn
Architects of Will: http://findmagiccards.com/Cards/AR/A...s_of_Will.html
Igneous Pouncer: http://findmagiccards.com/Cards/AR/Igneous_Pouncer.html
Jhessian Zombies: http://findmagiccards.com/Cards/AR/J...n_Zombies.html
Pale Recluse: http://findmagiccards.com/Cards/AR/Pale_Recluse.html
Qasali Pridemage: http://findmagiccards.com/Cards/AR/Q...Pridemage.html
Sanctum Plowbeast: http://findmagiccards.com/Cards/AR/S...Plowbeast.html
Valley Rannet: http://findmagiccards.com/Cards/AR/Valley_Rannet.html
Anathemancer: http://findmagiccards.com/Cards/AR/Anathemancer.html
Bloodbraid Elf: http://findmagiccards.com/Cards/AR/Bloodbraid_Elf.html
Enlisted Wurm: http://findmagiccards.com/Cards/AR/Enlisted_Wurm.html
Lorescale Coatl: http://findmagiccards.com/Cards/AR/Lorescale_Coatl.html
Behemoth Sledge: http://findmagiccards.com/Cards/AR/Behemoth_Sledge.html
Reborn Hope: http://findmagiccards.com/Cards/AR/Reborn_Hope.html
Slave of Bolas: http://findmagiccards.com/Cards/AR/Slave_of_Bolas.html
Bituminous Blast: http://findmagiccards.com/Cards/AR/B...ous_Blast.html
Dauntless Escort: http://findmagiccards.com/Cards/AR/D...ss_Escort.html
Enigma Sphinx: http://findmagiccards.com/Cards/AR/Enigma_Sphinx.html
Finest Hour: http://findmagiccards.com/Cards/AR/Finest_Hour.html
Madrush Cyclops: http://findmagiccards.com/Cards/AR/Madrush_Cyclops.html
Maelstrom Pulse: http://findmagiccards.com/Cards/AR/Maelstrom_Pulse.html
Wargate: http://findmagiccards.com/Cards/AR/Wargate.html
Dragon Broodmother: http://findmagiccards.com/Cards/AR/D...oodmother.html
Jenara, Asura of War: http://findmagiccards.com/Cards/AR/J...ra_of_War.html
Lord of Extinction: http://findmagiccards.com/Cards/AR/L...xtinction.html
Maelstrom Nexus: http://findmagiccards.com/Cards/AR/Maelstrom_Nexus.html
Sen Triplets: http://findmagiccards.com/Cards/AR/Sen_Triplets.html
Sphinx of the Steel Wind: http://findmagiccards.com/Cards/AR/S...teel_Wind.html
Thraximundar: http://findmagiccards.com/Cards/AR/Thraximundar.html

M10
http://findmagiccards.com/Cards/M10/Acidic_Slime.html
www.FindMagicCards.com - Nature s Spiral
www.FindMagicCards.com - Dragonskull Summit
www.FindMagicCards.com - Drowned Catacomb
www.FindMagicCards.com - Glacial Fortress
www.FindMagicCards.com - Mind Shatter
www.FindMagicCards.com - Mind Spring
www.FindMagicCards.com - Rootbound Crag
www.FindMagicCards.com - Sunpetal Grove
www.FindMagicCards.com - Baneslayer Angel
www.FindMagicCards.com - Master of the Wild Hunt

Zendikar
Kor Skyfisher: www.FindMagicCards.com - Kor Skyfisher
Mold Shambler: www.FindMagicCards.com - Mold Shambler
Expedition Map: www.FindMagicCards.com - Expedition Map
Explorer's Scope: www.FindMagicCards.com - Explorer s Scope
Arid Mesa: www.FindMagicCards.com - Arid Mesa
Emeria, the Sky Ruin (because why not): www.FindMagicCards.com - Emeria, the Sky Ruin
Marsh Flats: www.FindMagicCards.com - Marsh Flats
Misty Rainforest: www.FindMagicCards.com - Misty Rainforest
Scalding Tarn: www.FindMagicCards.com - Scalding Tarn
Verdant Catacombs: www.FindMagicCards.com - Verdant Catacombs
Day of Judgment: www.FindMagicCards.com - Day of Judgment
Luminarch Ascension (I don't care what Abe says, this is good for the essentials): www.FindMagicCards.com - Luminarch Ascension
World Queller: www.FindMagicCards.com - World Queller
Bloodchief Ascension: www.FindMagicCards.com - Bloodchief Ascension
Scute Mob: www.FindMagicCards.com - Scute Mob
Rite of Replication (this gets silly): www.FindMagicCards.com - Rite of Replication
Felidar Sovereign: www.FindMagicCards.com - Felidar Sovereign
Ob Nixilis, the Fallen: www.FindMagicCards.com - Ob Nixilis, the Fallen
Obsidian Fireheart: www.FindMagicCards.com - Obsidian Fireheart
Rampaging Baloths: www.FindMagicCards.com - Rampaging Baloths
Sorin Markov: www.FindMagicCards.com - Sorin Markov

Worldwake
Bojuka Bog: www.FindMagicCards.com - Bojuka Bog
Sejiri Steppe: www.FindMagicCards.com - Sejiri Steppe
Arbor Elf: www.FindMagicCards.com - Arbor Elf
Pilgrim's Eye: www.FindMagicCards.com - Pilgrim s Eye
Tectonic Edge: www.FindMagicCards.com - Tectonic Edge
Kor Firewalker: www.FindMagicCards.com - Kor Firewalker
Loam Lion: www.FindMagicCards.com - Loam Lion
Everflowing Chalice: www.FindMagicCards.com - Everflowing Chalice
Basilisk Collar: www.FindMagicCards.com - Basilisk Collar
Celestial Colonnade: www.FindMagicCards.com - Celestial Colonnade
Chain Reaction (I'm trying this, we'll see how it goes): www.FindMagicCards.com - Chain Reaction
Creeping Tar Pit: http://findmagiccards.com/Cards/WW/C...Pit.htmlKazuul, Tyrant of the Cliffs: www.FindMagicCards.com - Kazuul, Tyrant of the Cliffs
Lavaclaw Reaches: www.FindMagicCards.com - Lavaclaw Reaches
Marshal's Anthem: www.FindMagicCards.com - Marshal s Anthem
Raging Ravine: www.FindMagicCards.com - Raging Ravine
Stirring Wildwood: www.FindMagicCards.com - Stirring Wildwood
Stoneforge Mystic: www.FindMagicCards.com - Stoneforge Mystic
Terastodon: www.FindMagicCards.com - Terastodon
Thada Adel, Acquisitor: www.FindMagicCards.com - Thada Adel, Acquisitor
Admonition Angel: www.FindMagicCards.com - Admonition Angel
Comet Storm (this is practically the Ultimate Nightmare of Wizards of the Coast Customer Service): www.FindMagicCards.com - Comet Storm
Dragonmaster Outcast: www.FindMagicCards.com - Dragonmaster Outcast
Jace, the Mind Sculptor: www.FindMagicCards.com - Jace, the Mind Sculptor
Novablast Wurm: www.FindMagicCards.com - Novablast Wurm
Omnath, Locus of Mana: www.FindMagicCards.com - Omnath, Locus of Mana
Wrexial, the Risen Deep: www.FindMagicCards.com - Wrexial, the Risen Deep

Edit: added Acidic Slime and the Whole Shards block (for completenetss).