This is a bit of tooting my own horn since I am one of the administrators, but the Star Trek Expanded Universe wiki has been going for the better part of the past ten years.
It's available for all of your fanfic needs without any of the canon restraints of Memory Alpha or Memory Beta. If you want to archive your story, go right ahead.
Seriously, go right ahead. Unfortunately, with Abrams' film being the only major Trek production in the past five years, our membership has seen better days and we could always use more members.