That's quite the move! You should totally let us know how that's going by dropping us a line from time to time.
TMNT fanfiction is going strong on deviantArt and ff.net still. I also understand that people post a lot of stuff on tumblr, but I don't like that site. It's chaotic and hard to log on to.
Stealthy Stories moved to a new host and can now be found at Stealthy Stories ii. They are hosting the TMNT Fanficton Competition again this year, so when the nominations are posted in Feb. that will be a nice list of recommendations for someone to read.