TinyGL is a very small software only implementation of a subset of OpenGL for embedded systems. It has been ported to work on top of hotdog, which in turn makes it available to run on the iPod. Source can be found in my personal SVN repository at http://svn.so2.sytes.net/repos/ipod/tinygl/
No it isn't perfect and no it isn't super fast. Yes it does use software floating point, and no I don't plan to change it to fixed point. No you aren't going to be able to port any sort of intensive 3D application to it without expecting absolutely horrible performance. Yes, patches are welcome.