Pay what you want for these games, and dictate whether you want your money to go towards Electronic Frontier Foundation, Child's Play Charity, Introversion, towards the Humble folks themselves, or split any which way amongst those four! Plus, if you spend more than the average price paid (currently sitting at $2.96), then you also pick up two additional titles.
The Introversion bundle includes Uplink, Darwinia, DEFCON, Multiwinia, prototype gams Subversion City Generator and Voxel Tech Demo. The two bonus games if you go above the average are Aquaria and Crayon Physics Deluxe!
Go check it out, donate towards charity, pay whatever you want (just try not to be a Scrooge, ok?), and enjoy some great games!