Updated 30th of April, 2011
The latest public version of KarBOOM is version 0.3.7, and it is available at KarBOOM's page on IndieDB, the Indie Games Database, HERE. It's only about 20MB and requires no installation. All you need is a Windows PC.
KarBOOM is also available on Desura! The Desura client automatically updates games when new updates are available, and has a huge library of indie games for purchase (or for free, like the KarBOOM Open Alpha!).
This update improves adds more graphics options for those looking to improve performance, and makes some visual tweaks. It also fixes an issue with gamepads that don't have analog triggers. Create an account if you want to play online, and bash around random people you don't know! Or if you do want to get to know them, strike up a conversation on the forum. If no one's online, why not host your own game? Or play offline with someone you know -- that's where KarBOOM is at its best!