Bookmark Previews provides an interface similar to the one Coverflow does in iTunes and on iPods.
I'm not sure whether this is a better mechanism for working with your bookmarks, but it should have the same value as Coverflow in that it's a simple way to stumble upon items you've not looked at in ages.
Personally, I've almost completely stopped using browser bookmarks. Most of the sites I'm interested in have RSS feeds, so I follow them via Google Reader. The only bookmarks I have now are reference sites, like train timetables and my ISP's volume usage page.
There are precious few of those, now, too. As I've mentioned earlier, I now create keywords for any reference sites that provide a search box.
Thanks to Download Squad for the link.