First up, Shoo Rayner gives a nice, and simple, approach to the essential Santa Claus. You can use this as a start point for a few variations on the theme.
Then, from DrawKidsDraw we have:
For a more "realistic" take on him, we have this video from Proko:
And, finally, because I like his style, Chris of LethalChris Drawing gives us a warrior Santa:
So, a Merry Christmas and Happy Holidays to all!