A search engine is a vehicle to aid you in searching the web - no one engine covers the entire web, many overlap but it is best to try your search on at least three. Remember 60% of the web is invisible to search engines so try an invisible web directory or an online database  - freeweb or subscription to make sure you are really researching your topic thoroughly.
A topic directory is a collection of websites arranged by subject for you to browse or search through.
For an excellent understanding of the  types of search tools available and their limits, please see this berkeley university website on search tools: http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/ToolsTables.html

Here is another Tutorial on searching strategies from berkeley university library also worth reviewing: http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/FindInfo.html

The following is a list of a few recommended search engines and directories hot linked for your conveniance. It is not comprehensive, but a starting point.

Google
http://www.google.com
Yahoo
http://www.yahoo.com
Ask Jeeves
http://www.askjeeves.com
AllTheWeb.com
http://www.alltheweb.com
Librarian's Index to the Internet
http://www.lii.org
Clusty
http://www.clusty.com
infomine
http://www.infomine.ucr.edu/
ask.com
http://www.ask.com
HotBot
http://www.hotbot.com
Teoma
http://www.teoma.com
AltaVista
http://www.altavista.com
Gigablast
http://www.gigablast.com
LookSmart
http://www.looksmart.com
Lycos
http://www.lycos.com
Open Directory
http://dmoz.org/

Invisible Web Directories

Remember….over 60% of the internet is “invisible” to search engines. These are some of the best collections of information.
           
Direct Search site put together by Gary Price, a librarian and information research consultant. His page is nicely organized into searchable categories and is updated frequently.
Invisible Web Directory, put together by the aforementioned Gary Price and search guru Chris Sherman. This site is a directory of searchable databases, organized by subject.
The Resource Discovery Network has resources mostly from the placecountry-regionUnited Kingdom, and is extremely well-organized and very searchable.
The PlaceTypeUniversity of PlaceNameCalifornia at placeCityIrvine maintains InfoMine, an incredible resource that at last count included over 100,000 links and access to hundreds, if not thousands, of databases.
The Virtual Library is simple and easy to use, with annotated subject links. I especially appreciate the annotations because it helps rule out extraneous search time

There are many, many sites that are set up to dig into the Invisible Web. The University of Kansas's ProFusion meta search engine provides topical deep Web searches.

CompletePlanet.com is a directory of "over 70,000+ searchable databases and specialty search engines."
Most of the information on the Invisible Web is maintained by academic institutions, and has a higher quality than search engine results.
There are "academic gateways" that can help you find this information. The SJSU Academic Gateway is a fabulous resource that enables you to get into not only CitySan Jose public libraries, but the San Jose University library as well.
In addition, there are governmental databases such as
Ask Eric, which provide access to over 3000 educational resources (organized by category), and the