First, Welcome to the neighborhood - where is your farm?
one of the best resources is the Equiery - you can pick up a copy (its free) at The Surrey Tack Store (Rt 28 and Seneca right across from Harris Teeter grocery), the hardware store in Poolesville across from Bassetts, or Pooles Store. Quite frankly if you go in to any of those places chances are the folks in there would be glad to help you. If you go into the Surrey (which you will because its a great tack store) Lynn (owner) or Jaye might be able to give you some names/leads
There is a sawmill in Leesburg (just a short ferry trip away) that will load your truck full of sawdust for a mere $20.....it's wonderful if you don't mind an hour or so of shoveling once you get home....there is also delivery available, I think from seperate haulers, but the mill should be able to hook you up with someone.
Their number is 703-777-3600 - if you are going to go pick up bedding for yourself, it's best to call ahead, and certain times of the year it goes quickly - it's also sold as "white mulch" to landscaping companies...