If you're a command line master and you want to perform more powerful searches, check out YubNub. It provides a search interface to all the major search engines, social bookmarking sites, and other sites (Amazon, Wikipedia, and tons more) and uses commmand-line-like commands to perform searches of specific sites, but all from one place.

For example "gim Donald Duck" would return the results of searching google images (gim) with the search term "Donald Duck". Searching YubNub with the command "am sony ds3000" would return the results of searching amazon (am) for the term "sony ds3000".

There are thousands of commands (which may be too many), but this is a very powerful engine. You can also create your own search commands for almost any site on the web.