Here are a few to get you started...
Cocoa Dev Central (Bindings plus CoreData tutorials)
Cocoa Bindings Examples and Hints
Cocoa Lab Bindings Tutorial
Feedface Bindings Tutorials
Also you can get lots of information from the Apple developer pages (and from the Documentation window within Xcode), including Apple's bindings tutorials. And honestly, just do some Google searches, you will come up with a lot easily. OpenGL is cross platform, there is a ton of info on the web for it, though I would really suggest buying a book if you really intend to use it.
As far as Universal Binaries goes, the basics are pretty easy, you just open your project settings and check both i386 and PPC boxes for the Architecture setting, it will make a Universal Binary. The only issue I had was that I also had to set "Cross Develop Using Target SDK" to "MacOS 10.4 (Universal)" before it would work. Until I did that, it generated a bunch of errors. There might be a lot of finer points if you're porting stuff that depends on Altivec extensions, or if you need backwards compatibility or somthing, but otherwise just setting it up to recompile as Universal is trivial.