Actaully, I myself write fan fiction and am very involved with the Furuba fan fiction community. However, I write and involve myself exclusively in the YukixTohru fandom. Which is about all I can reccomend specifically. Here are some links to the YukixTohru authors who make my world spin in bright colors, sparkles, and flowers.
http://www.fanfiction.net/~ofamethysteyes (This is me, shamelessly promoting myself… 6_6 *sweatdrops*)
If YukixTohru isn’t your thing, then I suggest checking out the communities and finding something to suit your fan fiction desires. Usually, you’ll only find good fan fictions there. :D
Hope all this helps!