Play the 13 Indie games in The Potato Sack to help Portal 2 release early! See this page for more info:

Remember the Potato Sack? GlaDOS is apparently drawing "power" from computers playing games in the potato sack. For every collective 48 hours for one particular game, that game’s "power bar" goes up by 1%.

Potatoes multiply any progress gained by the number you currently hold. Even if you don’t own all of the Potato sack games, obtaining potatoes goes a long way to help the cause!