Supernatural Masterlist. All my Supernatural fic is here. Well, unless I haven't updated the list for a while, but stuff I haven't added yet will always be posted to my journal here, even if it isn't on the list yet. So feel free to scroll down through my recent entries looking for fic.
X-Men Masterlist. All my movieverse X-Men fic is here.
AO3. Most of my fic from 2011 onwards is here. It's all been edited for quality and typos, etc. It has basically almost all my Supernatural fic, all my Sherlock fic, all my Avengers fic, a little Doctor Who fic, some Good Omens fic, and some X-Men: First Class fic. It's where I now post all my stuff.
Fanfiction.net. All my older fic is here, which includes a heap of Harry Potter and Doctor Who fics, and some miscellaneous fic from other fandoms (eg. Star Wars, Diana Wynne Jones, plus a bunch of crossovers.) The older stuff, unless the reviews are in the hundreds, tends to have typos in it. I still post fic there occasionally, and any Harry Potter fic I do write does go there because all my Harry Potter fans are on ffnet, but mostly I post to AO3 now.