Since my “clean” installation of Leopard I’ve been making a point to avoid making a mess of my “personal information space.” One area of marked progress has been my bookmarks.
A lot of my time is spent demonstrating our products. In various situations I use Safari (of course), Firefox, Opera, and Camino. I use multiple browsers in order to demonstrate application compatibility, to exercise multiple authenticated user perspectives and to take advantage of browser-specific features. My demos (and most of my routine browser use) are based on a large set of bookmarks.
Until today I tried (and mostly failed) to keep bookmarks in sync manually. Not any more!
Today I found Safari Bookmark Exporter (SBE).
SBE is a free and simple utility that exports my Safari bookmarks into mutiple formats. It is smart enough to find my Firefox profile directory and render a proper bookmarks.html. I’ve been using this just for a day and I can’t imagine not having it!
Technology & Patterns 
Sounds cool, and likely the “right choice” for you and your environment.
I recently discovered Google BrowserSync Plugin for Firefox:
http://www.google.com/tools/firefox/browsersync/
While it won’t solve your problem of many different browsers, it’s very nice for multiple machines, all using Firefox. Also allows you to re-open any previously opened tabs when you quit and launch again.
Thanks for the tip to the Google BrowserSync Plugin – I’ll defnitely play with that as well.