Google, Yahoo, MSN are the common ones. The search for other SE's took me to some research. I found quite a few good ones. Here are some of them:
Vivisimo.com grokker.com rollyo.com topix.net Alltheweb.com
In fact you will find an article written by me on these search engines over
here.
Does anyone know any other good search engines? Some search engines cater to a specific niche. Please mention them too.