technical communities

Halfjack‘s recent mention of Usenet in a comment to
an Lj_biz post got me thinking about Usenet and LiveJournal
and the points where they intersect.

One of the things I’ve never really looked hard for here is technical
communities. I’m not sure why; partly because I hadn’t thought of it,
I suppose, and partly because a lot of them are pretty nontechnical
technical communities.

So, particularly for those of you who know where my affinities lie
(and for those who don’t, my bio
and interests
might help), could you recommend to me some
technical communities I might find interesting?