Buy bike shorts! I just came back from a longish ride (1600KM) and my ass actually doesn't feel that bad.
Solution? I bought those gay little padded bike shorts from MEC. Get the more expensive ones as they don't feel as much like diapers. They really keep your ass from getting sore.
Just a little bit of advice from a fellow rider.
Oh yeah, and pics from our Oregon trip will be up shortly.