I installed the nvidia cg package. And then I added the following entry to the rosdep.yaml file in visualization_common.

This is blank, what's the entry? In any case, I don't think it should actually be a problem of rosdep fails to find/install cg.

The make process for ogre_tools still fails for me like before (undefined symbol "_main").

I think the wrong-architecture errors you're getting are probably the root of your problems. It seems like your build environment may not be set up correctly.

What do:

file /opt/local/lib/libboost_thread-mt.dylib

and:

gcc -v

output?

Josh