Wow.  Two PDCs in a row.  

• MIX09 - March 18 - 20, at the Venetian Hotel in Las Vegas: is all about the Web.
• Tech•Ed - May 11 - 15 in Los Angeles. Tech•Ed is all about shipped Microsoft Technologies. Most of the tracks are presented by Microsoft product teams and industry gurus. If this is for you, be sure to check out the pre-conference seminars as it already has a really good lineup.
• PDC, a.k.a. the Professional Developers Conference, November 17 - 20, 2009 in Los Angeles, is all about Microsoft unveils its future, and it's the one that resonates best with developers. Be sure to attend this one.