First up, mark/space's "The Missing Sync" has been updated with support for the Treo 700w. I just bought a 700w last weekend and it's on its way to me now. I'll try it out with my Windows machine first. However, I'm a Mac guy (no, not that Mac guy from the commercials), so I'll definitely be trying "The Missing Sync" out and will let you know what I think.
Second, I see that Motion Apps mOcean music player for the PalmOS has also been updated with Mac iTunes synchronization. There's still no good way to listen to stuff you've purchased from iTunes Music Store on anything but an iPod, but if you're an mp3 user and use a Mac, you may want to check it out.
Seeing these apps got me thinking about the different ways I use my Sprint Treo 650 with my Powerbook. Bluetooth dialup networking 'just works,' as the settings for it are built-in to both my Treo and my powerbook. It's slow, but it is nice to have in a pinch (700p users, I covet your EVDO speeds). iSync automatically keeps the Palm's calendars, tasks, and contacts synchronized with iCal and Contacts - I honestly can't remember the last time I opened up Palm Desktop.
And a tip of the hat to our own Michael Ducker, who pointed me to what is going to now be my most-used Treo Mac utility. If you have bluetooth on your Mac, do the following: Open up /Applications/Utilities and drag the program called "Bluetooth File Exhchange" down to your dock. Now any file that the Treo can recognize can be sent just by dragging it to the dock! I tried out a .prc, a Word Doc, and a .jpg and they worked great. Even better, if you buy a Treo utility called ReceiveIt, you can specify that certain filetypes be sent directly to a directory on your expansion card. Using Bluetooth File Exchange is super easy, but, as Michael says, "slowish."
There are all sorts of resources for using the Treo with a Mac. Even if you have a PalmOS Treo, "The Missing Sync" is worth a look - it adds iPhoto and Memos synchronization as well as radically improving how the conduits interact with iCal and Contacts. You might also take a look at Palm's Mac and Treo page. Really, though, your best resource for using the Treo with a Mac is probably our very own Treo Mac Forum, where you'll find great threads like "Mac compatible software."