Before I say my choice:
Google & Altavista used to be one, but altavista split away from google when they didn't like google's tactics. Turns out that Google records your ip address for everything you search for, and isn't secure at all in keeping the ip addresses safe; a hacker can go and find your ip address.
after hearing that, I switched to MSN Search
most of the other ones (not altavista) put spyware on your computer