I went in search of an application that would synchronize my bookmarks. It needed to meet the following minimum specifications:
- Sync between Windows and Macintosh
- Sync bookmarks between IE, Mozilla, and Safari
- Sync between machines
- Automatic synchronization. If I have to perform a manual step, I'm not interested.
- Could not be an Internet-only bookmark storage service
- Good conflict detection and resolution
Sync2It met all of those requirements, and after using it for a couple of weeks with no real major issues, I bought it. Diigo and Google bookmarks were very good applications, too, but didn't pass some portion of my needs. I did email the author about some enhancements I'd like to see to make Sync2It even better. I'd encourage you to try and buy Sync2It. That way, maybe these suggestions have a chance of getting implemented. 
- While the Mac download doesn't say it, it does appear to work with Leopard.
- The Mac version only syncs with IE and Safari. We need Mozilla support on this platform.
- Provide an easy way to auto-launch the Sync2It application as a daemon when logging in.
- We need to be certain that Safari 3 is supported (both on Mac and Windows).
- It would be nice to have some kind of log to see the actual activity of a given sync.
Here's hoping this will let me focus on saving and categorizing bookmarks, as opposed to constantly leaving stray bookmarks around and needing that one bookmark on the one machine I'm not currently using!