Google Search:The most popular and, probably, the most powerful search engine. You can search text, graphic and other type of information. But be careful of how you donduct your search. You may be led to nowwhere for hours.
Yahoo Search: Another very popular site. Very useful but tends to be for the general users.
DOGPILE: If you have to go to different search web sites to find something unusual, you may want to try this website. It works by submiting your search queries to multiple search engines (such as Google, Yahoo, etc), then collate the results and present to you. So it goes to different search webt sites for you.
A9.com: One appealing feature of this site is its capability to help exclude (or include for that matter) certain major categories or domains of information. Thus it can help narrow down to specific types of information and put the search results under different categories.
Kart00: A metasearch engine that graphically displays a query tree and maps their relationship. It is very useful and powerful search tool once you are familar with it.
Clusty:Clusty queries several top search engines, combines the results, and generates an ordered list based on comparative ranking. This "metasearch" approach helps raise the best results to the top and push search engine spam to the bottom. It also groups similar results together into clusters.
PubMed: A good source for on-line medical and biological sciences literature search. It looks very clean and simple. But it may take a while to get used to it. It is not as intuitive as it should be.
HighWire Press: This is a powerful web page for search for published medical and biological information, similar to PubMed. It is a division of Stanford University Libraries. Although the layout seems s little busy, it seems more user-friendly and intuitive thant PubMed.