Apple Holding Second-Gen iPad Event
/The Loop just posted an invite from Apple for an iPad event in one week, on March 2nd. If I had to guess (and I don't really think I have to), we'll see an announcement of the second generation iPad, and likely the release of iOS 4.3, which has been in beta for the past month and a half or so.
As a left-field guess, maybe we'll get a preview of iOS 5, though Apple usually previews that as a separate event, however, the timeframe would fit judging from past preview events.