- comp.lang.c, using the c language, like ##c but more strict about topicality
- comp.std.c, describing, defining, questioning and refining the c language
- comp.programming.threads, threading mechanisms, in any language
- comp.unix.programmer, programming on posix, unix and posix/unix-like systems
- comp.os.linux.development.apps, specifically devoted to linux, for help with general unix/posix programming use comp.unix.programming instead.
There are quite a number of people that post to the Usenet newsgroups that are well worth reading, among them are (in alphabetical order): Greg Comeau, Thoman Dickey, Chuck Falconer, Clive D. W. Feather, Scott Fluhrer, Francis Glassborow, Doug Gwyn, Richard Heathfield, Lawrence Jones, Lawrence Kirby, Markus Kuhn, Kaz Kylheku, Ben Pfaff, P. J. Plauger, Dan Pop, Dennis Ritchie (yes, the R of K&R), Chris Torek and Dik T. Winter. And a host of others I'm sorry to have failed to remember. Each of them deserves a section here, but alas I am not super-human so will add them as time allows. Let's dig in right away though with one of my favorites, Chris Torek ...
Chris is one of the most readable and sensible posters, his responses are well thought out and make use of his decades of experience not only writing programs and systems in c but also the underpinnings (compilers and libraries), and some fine bits of wit as well. Search for articles by Chris via Google Groups -- here are some recent articles:
Another fine fellow, with a handy wit and plenty of experience and patience. The primary author of the book C Unleashed. And he can be found in channel! (Sometimes.) Until recently Richard has been too busy to keep up with Usenet (or IRC) so there's a sizeable gap in his posts -- he has recently returned -- but you can search for Richard's past articles via Google Groups -- here are some of the most recent articles available (okay, i say 'some' but only have the one for now -- fine, sue me!):
Here's another for you, an explanation of the signal() prototype, which we all know is a pig:
- How to interpret this declaration
(I don't think it's hit Google yet) (usenet)
From his web site  we have some handy pages:
- Casting do's and don't's: http://www.cpax.org.uk/prg/writings/casting.php
- Resources: http://www.cpax.org.uk/prg/portable/c/resources.php
- Getting string data from an input stream: http://www.cpax.org.uk/prg/writings/fgetdata.php (this one explains why not to use gets(), among other things)
Another brilliant contributor [more info here]