file sync software?

I just recently got a Mac, so I'm still looking for a few solutions...

I have one MacBook (intel) running Leopard, and two Windows XP machines. I'm looking for a recommendation on some file syncing software I can use on all three machines. Microsoft groove works decent for syncing between the two XP machines, but I'm looking for something that can work with my Mac as well.

All three computers will only need to be sync'd with each other when they are together (in the same room, or on the same wireless network). I also wouldn't mind plugging the computers into the same external HDD, and the HDD will update either the computer or itself with the most recent files.

Obviously, there are only certain folders/files I'm looking to keep constantly updated, not every document on the HDD

To give you an idea, iFolder (http://www.ifolder.com/index.php/Main_Page) would be perfect if the stable versions supported workgroup sharing and not just server-based sharing.

Any recommendations you guys could send my way would be great! Just reading through the forum has already been a big help.

Try out FolderShare
It has been bought by Microsoft but is still free to use. It has clients for both Macintosh and Windows.
Klaus

I'll give it a try - thanks