I've been researching field recorders. The MicroTrack M-Audio is the one I purchased about a month ago. It's a good combination of portability with advanced features. It's about $300, which includes everything needed to start recording immediately. Larger capacity flash memory card could be added to replace the 128mb card that comes standard. Depending on the record settings, you can get a lot of record time. Here's a link to an extensive review.
M-Audio shows list price of $499, but I found several online stores selling it for $300.
The M-Audio site has quite a few FAQs about Mac OS X questions and downloads.
I hope this is helpful. Good luck with the search and research.