User Interface (UI) enhancements attempt to improve the user experience and visual representation. Companies working in this area include; Snap, Live.com, and SearchMash. Another, Quintura, presents search results in a "visual cloud" that clusters results by meaning and intent. AskVox and Ms.Dewey use talking females to coach you through your search.

Technology advancements include; Hakia , Powerset , and Mindset , which search based on meaning or intent. Vivisimo and Ask.com present results in clusters that allow you to refine or expand your search. Findory, Jookster , Swicki , Collarity, and Rollyo do personalized or social search that present results based on your personal preferences or circle of friends. There are also a bunch of companies doing "tag" or "voting" based search...companies like Technorati, Digg, TailRank, and others.

Mobile search engines include; AskMobile, Boing, Google Mobile, Windows Live Mobile, Yahoo Mobile

Continuous search engines store your search terms and update you whenever something new fits your search. Examples are; Allth.at, Swamii and Searchbots.

Meta search engines submit your query to multiple search engines and present all the results on one screen. This has got to be the most over done, and marginal category in search. Examples include; Dogpile, CrossEngine, Gnosh, GoshMe, GoYams, Grokker, Ixquick, Mamma, Mrquery, PlanetSearch, PolyMeta, Pronto, Srchr, TurboScout, Whonu, and ZapMeta. 

Vertical market segment search has lots of players in each category;

Venture Capitalists, over the past 5 years,  have poured billions of dollars into search engine startups hoping to hatch the next Google. There are probably more than 200 search engines today, trying all sorts of different approaches to search. Still, nothing beats the traditional big three of Google, Yahoo, and Microsoft Live.