Image provided by Rockstar Games
According to USA Today and well multiple other sites :) Rock Star Game's Red Dead Redemption release date has been announced. Red Dead Redemption is a sequel to a 2004 hit Red Dead Revolver. You can read more about that here.

The official release date is:

...will be available on the Xbox 360® video game and entertainment system from Microsoft and the PlayStation®3 computer entertainment system on April 27, 2010 in North America and on April 30, 2010 internationally.

Source

The game's official website can be found here. Here's the official trailer for those of you that haven't seen it.