Google, Yahoo, MSN, Ask, and Gigablast all use their own search bots. The rest of the mainline search engines use one of those and then resort the results.
Ixquick is a metaengine which just takes results from other search engines and sorts it. For isntance is uses Yahoo, MSN etc.
The problem is with mainstream engines is they only return a certain amount of data, and a lot of it is duplicated, despite their claims. (Look at all the duplication with scraper sites of the Wikipedia).
Here are a few that I use. I’m not sure if they technically qualify as “search engines” since some of them are really specialized databases, but they’re still useful so what the heck:
[ul]
[li]Google’s various specialized searches, besides the major ones on the home page (some are very useful!): Products, Books, Scholar, and more.[/li][li]US Federal and State government pages: USA.gov[/li][li]Good deals on unnecessary consumerist crap: Fatwallet and Dealnews[/li][li]Images that look like another image: TinEye[/li][li]Second-hand prices on things: eBay Completed Items search[/li][li]Movies: IMDB, as mentioned before.[/li][li]Reviews for movies, music, and video games: Metacritic[/li][li]Travel (hotels, plane tickets, car rentals): Kayak[/li][li]Local businesses: Yelp[/li][li]Local classifieds: Craigslist[/li][li]Music (searching for a particular song): YouTube, Grooveshark, Last.fm[/li][li]Music that sounds like ____: Pandora[/li][li]Professor ratings for college and beyond: RateMyProfessors[/li][li]Website login info: BugMeNot[/li][li]Slang and idioms: Urban Dictionary[/li][/ul]