They're one of the early sites that did "pay what you want" deals. They tend to sell 4ish games for whatever you want to pay, and have bonus games that you get if you pay over the average (or some specific dollar amount). Nice part is they usually offer direct download or torrents of the games for windows/linux/mac and also steam keys. They used to be random indie games, but they now do "themed" sales. Seems the current ones is NeoGeo themed... Only a few of the current games come with steam keys.
Not sure if it's kosher but here is a link... https://www.humblebundle.com/ (mods feel free to remove as needed....)
Seems they have a normal store now too... only ever bought one of the bundles myself. They used to only happen once ever few months, but there is almost always one going on now.