Silicon Alley Insider offers the following guide:

Who’s In, Who’s Out?
There are 214 approved bidders. The ones you care about include wireless companies like AT&T (T), Verizon Wireless (VZ, VOD),  Leap (LEAP), and Metro PCS (PCS); cable firms Advance/Newhouse, Cox, and Cablevision (CV); satellite provider EchoStar (DISH), chip maker Qualcomm (QCOM), and Google (GOOG). On the sidelines: Sprint Nextel (S), T-Mobile (DT), DirecTV (DTV), Clearwire (CLWR), and Frontline Wireless, which dropped out of the auction earlier this month.

Who Wants What?
The big prize is the “C-block,” a huge swath of spectrum that has a minimum price of $4.6 billion. The big wireless guys want this so they can build a new wireless broadband network. This is also what Google is interested in. Smaller, regional telcos and cable companies will likely bid on the hundreds of smaller, regional licenses in the other blocks.

The FCC Spectrum Auction: The Cliff Notes Version - Silicon Alley Insider