<p>I've studied C programming in college some years ago and have developed some medium applications back then (nothing serious). Now I have to develop some more 'advanced' C applications (involving POSIX threads and RPC), but right now I'm a little rusty even with the basics.</p>

<p>Can anyone recommend me good online C reference manuals? This may help me get in tune faster.</p>

C standard library reference (both C89 and C99)
C89 library reference guide
GNU C tutorial
(more than just a tutorial, quite a useful reference)
I got these all from a previous similar question on SO.  I would like to credit the original posters, but unfortunately cannot seem to find that question.