Personally, I prefer using Google Sketchup
as my CAD program. As a cad program, it's incredibly user friendly (relatively speaking), and it also lets you be very precise. You can use it to make anything (theoretically), but I've only used it to design structures and vehicles so far.
It doesn't have any easy sharing abilities from what I've seen, but It's easy enough to make pics (or vids, with the right software) using it.