Ben Adams is the creator of Misfit's Journey which is an autobiographical tale with 3d art.  He has been placing ads with non-webcomics websites where he thinks the audience would become fans of his webcomic.  In another post, he further explains his thinking about where his webcomic's appeal may lie.

A no-brainer perhaps, but one all creators should think about before spending money on advertising.  I have no data to back it up but it doesn't seem farfetched to believe that there are still a lot more potential readers out there that haven't heard of webcomics at all then are actively reading them today.