I'm having trouble saving my mp3s on my 8800. I download them by bluetooth from my laptop but my 8800 won't let me save it in any folder other than the ringtones folder no matter what I do. How can I force the 8800 to save my mp3s in a folder other than ringtones? Thanks.

Try this if you have a microSD card...

How do I add media files to my microSD card? - BlackBerryFAQ

I found it much easier to plug in with the included USB cable, then when the 8800 asks if I want to use it as a drive, I say YES. The 8800 can then be navigated like any drive and you can drag over your mp3s where you want them.
This works just as well in Linux as OSX, FYI

When I plug in the USB cable to my BB and my Powerbook Mac, the computer doesn't recognize anything.

I'm having a problem with the same.

Setup with desktop manager first...with my 8800, it does not connect sometimes when using USB cables other than the one that came with the BB.

When I plug my 8800 into my PowerbookG4 , the 8800 asks if I want to turn on Disk Storage Mode. 'Yes' gives me an icon on the desktop.