I really want to start learning C but haven`t a clue where to start.
Don't. Learn C#, Java, Python or Ruby instead. Hell even Visual Basic is probably a more useful language than C. Also what are the different versions of C and what merits do each of them have.
Basically there's ANSI C and "Everything else". The main advantage to ANSI C is that it's standardized. Also how hard is C to learn over things like B3D\BMax?
Not particularly. Getting good at it is the hard part - learning it is easy.