http://hypnopics-collective.net/cpg132/index.php
I know this site was briefly mentioned earlier, but I just wanted to point out that while most of the site is dedicated to hypnosis/mind control, a few of the user galleries have quite a bit of evil conversion stuff.
You have to sign up with an email address, but it's worth the effort.
jnightshade2 - Lots of vampire and demoness TF
Freezeframe - Not as densely packed with good stuff, but still a fair amount
bstyles - Has a couple of pics of interest