Also be sure to try these links for more on Conlangs and conlanging:
The constructed languages email list par excellence is, of course, CONLANG itself. It is a listserv administered from Brown University, and you must sign on to the list via Brown if you wish to participate. Although Yahoo has a partial archive and a mail list that seems to be Conlang, you can not participate in the group by subscribing to Yahoo's group.
In order to subscribe to the Conlang mailing list, send an email with the message that says only "SUBSCRIBE CONLANG _your name_" and without quotes to Conlang at:CONLANG
You can also access Brown's listserv via web interface here. Here you'll find the archives and you can edit your membership.
Yahoo is certainly the best locale for the various conlang and conculture subgroups. The following are direct offshoots of Conlang:
West Asian Conlangs
East Asian Conlangs
Other conlanging lists, not directly related to Conlang are:
On Usenet, try alt.language.artificial.
In Spanish, there are two conlang lists:
In French, there is one:
Lastly, if international auxilliary languages are of interest to you (Interlingua, Esperanto and their ilk), then give the Auxlang list a try: here. You can see the archives and edit your listserv membership.
For the conculture oriented, try these lists: