In beta testing, Quintura.com is a cloud-inspired search engine that offers an interesting way to search for relevant results.
By typing in a query, Quintura returns a cloud of related keywords. A user can then mouse over any of the terms to get a new, expanded cloud of words that further define your search results. Click on a word and the search continues to narrow, revealing more related terms. All the while, search results are continually updated and listed towards the bottom of the page.
A user can also select to exclude certain terms, manually refine the search by double-clicking on the page, email search clouds to others and save search results for later viewing.
It's really an interesting tool and a nice way to quickly refine a search based on related keywords without having to continually type in new queries.
I would like to see it react a little faster, however. The movement and appearance of the page is sometimes jerky and some terms begin to overlap each other, making it a bit confusing. I expect to see further refinements sooner than later. Either way, it's definitely worth a look.