It's tough to talk about the Humble Indie Bundle without using words like "awesome" or "amazing". The deal works like this. Pay what you want, and get 4 amazing indie games--Amnesia, Limbo, Psychonauts, and Sword & Sworcery. Pay more than the average everyone has paid to date (currently, it's $7.72) and you get Bastion too. Also, you get the soundtracks for all of these games--and they're all good.
When it's time to check out, you decide how much you want to pay, and then you decide where you want your money to go. You can give it all to the charities (the EFF and Child's Play), all to the developers, all to the people who make the Humble Indie Bundle, or any combination of the three. After you do that, you'll get a code that unlocks both standalone versions of the games you can download for your OS of choice, as well as steam codes to activate the games on Steam. It's an amazing deal.
It's the best deal going this weekend for games. Bastion is my personal favorite game from 2011, Psychonauts is one of the weirdest, best platformers from the last decade, and Amnesia: The Dark Descent is terrifying by all reports. I don't know, it was too damn scary for me to play.