For Usenet nerds, there's a good forum about the Japanese language:
sci.lang.japan
Apparently they prefer if you don't access it through Google Groups, but you can do it anyway:
http://groups.google.com/group/sci.lang ... schg&hl=en
Good place for any technical grammar questions (it seems to be frequented by some Japanese linguists, including at least one author of various Japanese grammar books).
