If you're in to lighting photography with off camera flash, or even lighting photography in general, then I can't think of a single better seminar to attend then the one being put on by David Hobby (the Strobist) and Joe McNally!
Just announced today on their respective blogs, David and Joe will be touring the entire country from March through April sharing their immense magnitude of lighting techniques with off camera flash. David's class will be focusing on doing things the "manual" way while Joe will be guiding you through the powers of TTL flash photography.
The name of their tour is Flash Bus Tour 2011 and you can find out more details by checking out the website, including more info about David and Joe, tour dates, prices and what will be covered.
While there aren't that many seminars I would care to attend, I will be first in line to see these guys. I am honestly excited and can't wait to attend one of these! Hope to see you there!