EmuDevs and YouTube Release Only.
--Edit: Modcraft too.
UPDATE: -- I've put together a Tool to automatically search for M2/Skin files and convert them on the fly rather than having Manual intervention:
This is mainly for folks that have done manual hand conversions of Cata/MoP M2 and Skin files to WoTLK 3.3.5a., otherwise this script will prove little use for you.
Here is my Video Vlog on the script as well as some background information and some tips. If you're interested.
My Script and DLL Files to make Mjollna's converter work:
Mjollna's converter link over at modcraft:
My Old Tutorials for manually hand converting m2 and skin files: