I'd like to test out booting another operating system on the wii. Familiarity is with open firmware when it comes to powerpc machines. Will it recognize an hfs partition on a cd and boot from it?

Wii will not boot any other operating system automatically. The only way to do something like that is to port the OS to the Wii and run it as homebrew. For example, there is Wii Linux.

Also, the Wii can't read CDs, only DVDs