UPDATE: if you contact HiB support via Humblebundle.com they are giving out Desura keys for Blocks That Matter. I hope that once we are supporting Voxatron and Binding of Isaac we will have keys for them also, but no promises there. Big thanks for the humble guys for showing their indie heart!
This is old, but still current. You can grab three games for any price you set yourself. The main dish is an alpha version of Voxatron. All three games are crossplatform as usual and are available on Mac, Win and Linux.
Be the first to tackle Voxatron -- a voxel-based, old-school-gone-new platform shooter. Pick up your trusty pea gun and shoot your way through more than twenty challenging areas. The included Voxde level editor grants you the ability to create mind-blowing new environments to share with the world. And, as a customer of the Humble Voxatron Debut, you'll receive access to all of Lexaloffle's future updates to Voxatron.
Dive into a twisted basement dungeon in The Binding of Isaac. Get ready for a delicious brew of randomly generated, Legend of Zelda-esque dungeons; Robotron-esque run-and-gun; and action-RPG progression. The recently launched Halloween update adds a ton of content -- a new chapter, new bosses, new enemies, new items, a new character, a new ending, and more!
Learn new tricks with tetrominoes in Blocks That Matter. In this award-winning, charismatic, platform-puzzler mashup, you play as the Tetrobot, a plucky robotic drill that assimilates blocks of varying materials and properties, like sand, wood, stone, obsidian, iron, and diamond. After absorbing blocks, you’ll need to recreate them in various tetromino-shaped patterns to solve puzzles and traverse levels.
If you haven't bought the newest bundle yet, there's still some time (7 days at the time of writing this).