San Jose based LeapTag is part bookmarking (like del.icio.us) and part discovery (like StumbleUpon). It’s a good way to keep track of websites that you like using tags, and it’s also useful for serendipitous discovery of new sites you might like, based on the things you’ve already bookmarked.
Usage occurs through the browser via an IE or Firefox plugin There’s a sidebar that lists each of the tags and associated bookmarks. You can easily skim through tags to find your bookmarks (although it is slower and less organized than Del.icio.us via their Firefox plugin). Frankly, if all you want is a bookmark manager, this is not a good choice.
Like StumbleUpon, though, LeapTag will present new sites to you that you might find interesting.
StumbleUpon asks users to vote on sites they visit, and then compares those up or down votes to the votes of others. By analyzing the vote streams of many users, StumbleUpon can throw you to a random site with a fair degree of confidence that you’ll like it.
LeapTag does this as well, but suggests sites only when you click on a particular tag in the sidebar. When you do that, it shows you your bookmarks for that tag in the sidebar, and also shows you additional sites that you might find interesting. Results are delivered based on the voting patterns of you and other users, but isn’t limited to sites bookmarked with LeapTag. They also scour search engines and RSS feeds for additional content that might be relevant to the tag. If you want to see it visually before trying it, see this video of their presentation at the DEMO conference last year.
I found it to be very useful for randomly discovering sites based on a descriptive tag. I bookmarked a few gaming sites and then looked at what it recommended. The results were good.
It does, however, require some work and organization to get things going. If you use another bookmarking service, it will be awkward to bookmark sites to both services.
I could not get the plugin to work properly on my Mac, although it worked fine on my Windows XP test machine.