In case you haven't checked your steam account today, I'd like to point out that if you don't have half life 1, 2 or episodes, now is the time to buy! Or, if you don't have any source games, I would reccomend the valve complete pack - every game valve has ever published for 52 pounds! That includes Orange Box, L4D, all the original Half-life games, Counter strike, Day of Defeat and more.
http://store.steampowered.com/