State Farm is your best bet, Progressive is a complete joke on BUSA rates. A couple other motorcycle only places (I've heard, never used) offer good bike rates but you will have to have excellent specs (no tickets, 700+ credit, MSF-course, etc.).
Whatever you do, DO NOT buy it on a credit card and get liability only. I've seen to many people do this and get screwed...
(If you are military under the old system you can't beat USAA but if this is your first bike with them, you no longer qualify.)