You can probably consider this a "Groups Spotlight" - Berdan's Sharpshooters are actually several groups representing one of the arguably most elite units of the American Civil War. The first organization I found, Company C, seemed to be the one that was the most together, so I surfed the other sites from there. This site is actually chocked full of information and easy to navigate, and pleasing to the eye to boot. It was updated within the last couple of months, decent for a reenacting site, so I'll say they where within my DIGM criteria for a good site.
The next site's caveat was that it's still under construction. Also it doesn't represent a group per se - it's a portal for the rest of the Berdan's groups around the county. This is the Berdan Sharpshooters Preservation Association, Inc. site. When it is done, I think it'll be a great site to find out more about the historical unit and the reenactors units around.
Another Berdan's site on the west coast is Company D from Oregon. They seem to be pretty active in their own neck of the woods. The site can use a bit of spiffing up, but it does convey basic information well. A re-organization of the navigation would be super.