There’s a few of my captions where I use gifs, but they aren’t ‘morph’ gifs by any means. There are a few sites that do morphs and stuff on tumblr, but I don’t seek them out myself. I guess I prefer imagining the TF more than trying to render it visually. Here’s two I know of, but I don’t know if they update very regularly.
http://changemechainme.tumblr.com/
http://m2mmorph.tumblr.com/