Last time I tried jumping on to a few newsgroups it was like walking into an abandoned city. The last posts on once active groups are years old, not counting the random spammer.
By the way, I think it's absolutely amazing that one can access the same discussion over several protocols (NNTP, email mailing list, and often HTTP) without losing any functionality.
By using HTTP I lose a lot of features! I can't filter (both for removal as well as for highlighting) as I need (i.e.ignore some flame war threads or highlight messages to me), I can't work offline (while there are less situation where that is needed, but can still be useful when loading on the side and then having low latency while looking through messages) etc.
However mail and nntp never really got the spam problem solved and development of "nice" clients basically stalled last 15 or so years.
SynchroNet today has crazy multiprotocol support.
comp.unix.shell Unix utils, awk, shell scripting.
comp.lang.c C programming help
comp.lang.c.moderated Ditto, but with less nuts
alt.os.linux.slackware Slackware users.
rec.arts.int-fiction (text adventure game creating)
rec.games.int-fiction (text adventure game announces/discussions)
rec.games.roguelike.nethack Nethack (and Slashem by extension).