If I understand you correctly, you are looking for a web-based calendaring system that you can then synch with your Palm Pilot. Yes?
To do this on the Macintosh, all you need to do is obtain a copy of latest Now Up-to-Date and Contact and enable the calendaring server software to be published on the web. This requires that you have your own server, unlike anyday.com. However, the software works very well and provides you not only a nice Synchronization program but also web-accessible calendaring.