http://www.humblebundle.com/ Braid, Cortex Command (which is under development/being updated, still), Machinarium, Osmos, and Revenge of the Titans (which is exclusive to this bundle).
All for charity, all for your own set price. not sure if you can get them for free, but you can definitely set it very very low, so long as you don't mind ripping off charity too much.
update: 5 more days till the bundle ends, and you can now add them to your steam account (achievements and the like)
there's a link on the download url, if you've already bought them. if you haven't, it's only more incentive, as it's optional.
