Although I've posted something like this before, I'll do it again. With my frustration of not being able to visit the Authentic Campaigner Website, which is down for repair, here is a listing of places to visit and talk to other reenactors.
One of my favs is the Camp Chase Gazette forums. This is a very user friendly forum, although getting to it is slightly frustrating. You have to link into an interior page before you see it actually listed on the lefthand side navigation. The guys here are great, and have a knack with mentoring reenacting newbies and not-so-newbies such as myself.
Arguably the premier "every reenactor" forum is CW Reenactors. This is actually a great site to talk about Civil War reenacting in general, and for new reenactors to fill in the gaps in their knowledge. You typically run into all reenactor types, from "mainstreamer" to "campaigner". It has the largest reenactor pull of any of the forums, and if you post a "group wanted" ad, you'll get responses for weeks on end.
Definitely considered the most controversial and highest quality messageboard is the Authentic Campaigner forums. This site caters to the "campaigner" type of reenactor - the ones who push the envelope has far as authenticity. But beware, this site is not newbie friendly, or at least not lazy newbie friendly. It is highly recommended that you "lurk" on this site for a few weeks before actually posting anything. Also use the "search" function and try to answer any question for yourself before posting. This site is one of reenacting's best sources of information, but do not take everything mentioned on the forum (as with any forum) as gospel truth.
Another one I just found tonight is the West Coast Campaigner. The quality of the conversation is good and it's set up similar to the Authentic Campaigner, except not as feature rich or graphical. But it still conveys a good amount of info for any reenactor, and has a friendly look and feel to it. Worth checking out.
If you've 'jined the cavalry, then you may want to join The Civil War Cavalry Forum. Discussion here is about... you guessed it, the cavalry. Very useful site to find out about proper equipment and cav-friendly events. Discussion also covers horse-drawn artillery and wagons, which we really need to see more of in the Eastern part of the hobby.
A low-volume forum is the sub-topic messageboards in Civil War Talk. Not too much happening here, but the posts are current, with posts on par with CW Reenactors. Be forewarned that these boards are well-moderated and the mods take no guff from surly bros who want to pick a fight on a small forum.
A neat little forum geared toward reenactor teens is Teen Reenactors and Historians. Conversation cuts across anything Civil or reenacting related on this forum, but from a uniquely teen perspective. A site deserving of some exposure and contribution.