do this: http://www.mozilla.org/products/firefox/smart-keywords.html

you could probably write a Greasemonkey script to integrate other search results into one view (ie mix in Bing results into Google results ect)

Creating your "own" opensearch provider for any search engine on the internet is ridiculously easy.

In fact, going to any search engine which allows you to add a search provider should give you a simple enough template to work with. Just customize the URLs used there and point it at this thing. Then make a html file with the needed html-header field and you are good to go.

It should be a 5 minute job tops.