UPDATE: still available, look under Washington DC (but valid nationwide)
You can get 5 Blockbuster Express Rentals for just $2! That's like $0.40 per movie rental! Plus, these codes are good until 2013, so you're bound to have an occasion to use them!!
This would even make a nice little birthday present to include in a card or an awesome surprise for a college student in a "thinking of you" card or care package!!
To get this deal, just sign up for a new account with Groupon, then look under DC (under "more cities" at the top).