Couldn't find a thread on it, and I figured it's worth a mention like the last one received. It just got a week extension, so better now than never.
Basic jist, like last time, donate what you please, and get access to the advertised games for PC/Mac/Linux. Best of all they just added the ability to redeem applicable games for either bundle on Steam, which is cool on Valve's part.
But yeah, donate what you want, a penny, five bucks, one hundred if you're crazy, or you can also be a dick and just borrow someone elses' key as all the titles are DRM-free. ;/
http://www.humblebundle.com/
I put in $5 like I did on the first bundle, with the majority of it towards the devs, the rest towards Child's Play. Braid & Machinarium are the worthwhile mentions this time around if you for some reason have never got around to them already.
XI Wiki

