http://www.gog.com/Currently has a promotion where they're going over the last 30 or so years and offering one associated game (or bundle of games) per year at 80% or so off. Each game has a clock and is counting down from 90 minutes until it reaches zero at which point the sale for that game ends and the subsequent year starts the process again. Whenever the game is bought, +3 seconds are added and users can likewise add or subtract a second on each game.
Right now it's the year 2000 and they've got Deus Ex GOTY edition up for 1.99 (8 dollars off). Obviously peeps have missed out on 1984-1999 but there's still 2000-2013 to go.
When does the promotion end? No idea. It depends on how many people are buying the game. People are predicting Deus Ex will be up for a few hours but the sale itself will probably be done in a day or two.
http://www.gog.com/news/drmfree_time_machine_saleEarlier I picked up Police Quest 1-4 and Wizardy 5+6 for 3.50 total. (Not that I don't already have a big enough backlog).
EDIT - Deus Ex is done and now it's on to Gothic. Some 3rd person action RPG?