Yeah, there's lots of it, but you wouldn't be interested in most of it. The majority of vintage TMNT manga is nothing but adaptations of episodes of the Fred Wolf cartoon with pretty lousy art.
Here's a rundown of the various TMNT manga series as well as a history of the line in Japan (though you can just skip to the manga section if that's all you want to know about).
You can read the entire Mutant Turtles Gaiden series
here. It was a single volume, 4 chapter series of original content and its amusing, if anything. Art's pretty good and the story is a nice hybrid of light-hearted action and goofiness.
There's also a 3 volume Super Mutant Turtles series that's made up of original content. I intend to translate it, some day, but I'm waiting until I can get my hands on the first volume (Alex Winters owns volumes 2 and 3, and he provides me with the scans I need for translation, but neither of us can find Volume 1).
Anyway, hope that helps. Alex has lots of scans of the episode adaptation series if you'd like to see what that art looked like (but it isn't anything to write home about).