The Fair will be streamed online through Ustream. It's free, and there's no reservations or passwords. You can ask questions through the chat function, or tweet your questions to @usnatarchives #genfair2013.
Experts from the National Archives will be discussing Native American and African American history, immigration, Civil War pensions, U.S. Colored Troops, and Navy Deck logs.
We hope to "see" you there: http://www.archives.gov/dc-metro/know-your-records/genealogy-fair/
Recorded sessions will be available online after the event.