A webpage with a list of free games for Windows
It was quite old (archive.org suggests it's been there since 2008), but interesting piece of information.
Note that it ceased to exist at the end of 2015, but its latest version is still available via archive.org and archive.is.
It's thanks to this list I learned about such games as Nexuiz, World of Padman, Torus Trooper, Bontago, Scorched3D, and learned that Grand Theft Auto 2 was available for free download for some time (it's not available at the moment of writing)
So if you're bored (and have Windows), there's a whole list of entertainment waiting for you!