Tons of XBLA games on sale currently. First and foremost: Shadow Complex is on sale at 560 MS Pts (1200 normally) which I highly recommend to anyone, especially if you're a Metroid or Castlevania fan, and especially at that price.

http://www.cheapassgamer.com/forums/showthread.php?t=264333

June 14th - June 20th: "Summer '09 Redux" GOLD MEMBERS ONLY
-Marvel vs Capcom 2 - 560 Microsoft Points
-Shadow Complex - 560 Microsoft Points
-Splosion Man - 400 Microsoft Points
-TMNT: Turtles in Time Re-Shelled - 400 Microsoft Points
-Trials HD - 560 Microsoft Points

June 16th - June 22nd: "E3 Inventory Blowout" THIS SALE IS FOR GOLD AND SILVER MEMBERS
-A Kingdom for Keflings - 400 Microsoft Points
-Alien Hominid HD - 400 Microsoft Points
-Banjo Tooie - 800 Microsoft Points
-Bionic Commando Rearmed - 400 Microsoft Points
-Bomberman LIVE - 400 Microsoft Points
-Castle Crashers - 800 Microsoft Points
-Castlevania Symphony of the Night - 400 Microsoft Points
-Contra - 240 Microsoft Points
-Crystal Defenders - 400 Microsoft Points
-Geometry Wars: Retro Evolved 2 - 400 Microsoft Points
-Magic the Gathering - 400 Microsoft Points
-N+ - 400 Microsoft Points
-Panzer General - 400 Microsoft Points
-Portal - 800 Microsoft Points
-TMNT: 1989 Arcade - 240 Microsoft Points
-Uno Rush - 400 Microsoft Points
-Vandal Hearts: Flames of Judgment - 800 Microsoft Points
-Zombie Apocalypse - 400 Microsoft Points