Both Bikes Unlimited and Blackwater are fine shops. I shop at both of them, they can hook you up. There are plenty of routes around the area, including Altavista. Check out
www.811velo.com which is yahoo forums for the local riders. There are usually plenty of rides going on. There is also the Central Va Bike Festival on May 17th if you are going to be around. It's a great route to see the best of the area.