Fan Art is extremely popular here on deviantART, but a lot of people elsewhere - or "mundanes" - don't really understand it or know much about it.
To that end, I recently wrote a webpage About Fan Art and Fan Art's History
. Because even many fan artists today don't really know about the history of fan art and its importance in the fan community. Fan art can also have tricky legal issues to deal with that I also address on the page, along with including links to some of the best websites on line for finding fan art.
Anyway, if you're interested, please check out my page on fan art
for more information. And leave me a comment with a link to any great fan art websites I've missed including there!