I've already linked to The Sykes Regulars site, but I think it's well worth noting it again. So far, it is the best group site out there, combining graphic beauty, information distribution and all-around usefulness to the reenactor.
This site has been kicking around for quite some time too, and had me hooked in wanting to do a Regular Army impression for quite some time. I can say that some of my present thinking has been shaped from what information I have read from the Sykes Regulars site. I hope these guys keep up the great work into the future.