CUDA C tutorial websites

I am new to CUDA C.
So I have to know more about CUDA C programming.
Some concepts are not easily understandable.
I need CUDA C programming online tutorials website.
Will you help me ?

the entire series is pretty useful

I found the provided documentation (the CUDA programming guide && best practices) and the SDK examples to be the best way to get a feel for CUDA; many of the articles/tutorials online are somewhat dated as of now, although admittedly they can still have useful information (the Dr Dobbs article(s) mentioned by cbuchner1 are excellent, despite being written for CUDA 3.2)