[Update] If you weren't enticed enough, the Humble 2K Bundle now also includes the X-COM: Complete five-pack which comes with Apocalypse, Enforcer, Interceptor, Terror from the Deep, and UFO Defense. The second-tier of titles, which is sitting at just $8.05 (at the time of this update), now has 8 games.
[Original] The Humble Bundle is forging ahead once more with the Humble 2K Bundle, bringing together eight (or more!) games together for a wondrous pay-what-you-want deal. Not to shabby for $209 worth of games, all while supporting 2K Games, the Humble Bundle service itself, and various charities like Action Against Hunger and the American Red Cross.
Paying just a dollar will net you BioShock, The Bureau: XCOM Declassified, and The Darkness II for Steam, but hopefully you'll be able to pay about $5-6 ($5.32 at the time of this writing) to unlock three more games: BioShock 2, Mafia II, and Spec Ops: The Line. For me, Spec Ops at that price makes the humble a steal, but I'll let Heath Hindman talk about why when his Most Interesting Gamer feature goes live later today.
Paying $20 or more will unlock BioShock Infinite and XCOM: Enemy Unknown, which would mean you would be paying about $2.50 each for the eight games available. That said, you have two weeks to wait for the deal to end, and by that time, more games will unlock on the second tier.