Mr. Excel is a great online resource. If I'm stuck on someting, I generally go there first.
For an overall course, I'm not sure. I find excel works best if you just tackle the problem in front of you, which leads to learning other things. Also, working with others generally gets you tricks you never thought of - I'm a pretty advanced user, but have learned some short cuts from some of the more basic users.
You can PM me if you get stuck on something too.