I too have been thiinking about learning C... our uni had a few tutorials on it (in fact, it had thousands of 'em), but you need to be a student there to use them.
You're probably best off with a book instead of learning from the web anyway. That way when your buggy rubbish newbie code breaks the compiler which breaks Windows which then destroys your house and makes your cat explode, you won't have to go find it all again...
I've been told that, from a reasonable level of mathematical knowledge, it takes about 3 years to start writing good code, but you should be able to get the basics after as little as six months.
Urk.
C = bitch.