GameTap is a very unusual digital distribution site. Rather than individually buying games, you pay a flat monthly fee ($5 at the moment as part of a promotion) and get EVERY game in their library. They have a lot of older games, but also plenty of new ones (it’s usually not the cream-of-the-crop mainstream games, mostly hidden gems)
Since the amount monthly is less than most MMOs, it’s a pretty enticing offer. If you sign up before January 2, the price will never go back up to the standard $10/mo. for you.