I've been down this same road, having OSX but wanting to use AvantoGo. (which you must use OS9 or Windows) I did it thru Virtual PC for a while before I discovered "iSilo".
Step one: get the iSilo document reader ($18.00 shareware) for your Palm at PalmGear
Step 2: Get the iSiloX document converter (free) for your Mac, which works with OS9 or OSX, also at Palmgear
Step 3: Once you get those installed, visit the mobile section at Turcic.com and download the HUGE iSilox document list of Palm compatible sites. Copy and paste the ones you like into an iSilox document of your own. iSilox will convert the sites for your Palm and put them into your user folder, ready to sync.
It's really fun, once you get the hang of it, and the selection blows away AvantGo. My favorites are BBC World News, Slate.com, Cnet news, etc. Turcic.com even has a forum, much like this one.