I found that a lot of the addons for WoW are supposed to be Mac compatible, but I believe the problem is that most files downloaded are zip format that Mac OS X's native decompression engine doesn't handle cleanly, which will cause the attempt to fail. So, here's what should remedy the situation.

If you goto

http://www.macobserver.com/columns/slacker.../20050812.shtml

then scroll down there will be a link to download Aladdin's StuffIt Expander utility, which works the same as WinZip or whatever that program is called. This will enable most Ziped files to be expanded just like Winzip is supposed to do, then you just drag the addon into the ..worldofwarcraft/interface/addons file. Also, the person who wrote the information on this webpage is a Mac user playing WoW, and the addon that he uses is CTMod. Now, I'm currently working on getting this addon to work on my Mac, and hopefully, here shorlty to be exact, I will have this addon working fo my Mac version of WoW. Update soon!

Lleo

If your problem is extracting .zip files I suggest using this:

http://www.edenwaith.com/products/guitar/

It's a free program that works wonders and I used to love when I played wow.