What is a good free bookmark synchronization service?

I currently use Xmarks to sync Firefox at home on my Mac with Firefox at work on Windows. I also like to keep Safari at home in sync, and Chrome at work in sync too. I have been using Xmarks since it was Foxmarks, but lately it has been letting me down by erasing random bookmarks, and completely duplicating everything else.

So, what do my fellow nerdy Flutherers do or use to keep their bookmarks in sync across browsers and operating systems?