Well? The vorbis site only has windows and unix versions. Are there any ways for mac users to be able to convert .mp3s to .ogg?

The easiest way would be to convert from mp3 to wav, then from wav to ogg. Since Mac os X is a unix, you can get all the required programs (although you might need to fiddle with some Makefiles to compile them properly).

First, you need something like mplayer that can turn a mp3 file into a wav file. Then, simply use oggenc to turn it into an ogg file. Simple really. Happy compiling.

OggDrop can convert from aif and mp3 to ogg.