Well, there a few in the Monster Manual, and it is fairly easy to convert any 2nd edition ones you find laying around. There is a D20 product, something about Etherships and Dinosaurs, but I think it is a dead project, that might have some new conversions. I am also compiling a living jungle creature catalog that will have a numer of dinosaurs I found or made, but that will not be ready for awhile. You should go to:
Well, thre were a few threads about them in Rules and House Rules.
Unfortunately, they're on the old boards (and therefore not available), so here's a link to my treatment on sauropods.
I haven't worked any further on the ankylosaur that was discussed.
Uh...that Living Jungle link doesn't go to anything at all related to D&D, I'm afraid. Here is the official RPGA Living Jungle campaign page: http://www.wizards.com/rpga/LJ/
The Broncosaurus Rex stuff looks interesting and strange, to say the least. Although I'm not so thrilled about North vs. South on an interplanetary scale, the idea of raptor tribes makes me salivate. Of course, the book lists them as NPC only, but I say poppycock to that....