In Firefox I use bookmarks with keywords to do most of my common searches, I don't remember if some of them are configured by default still, but I think they used to be.
Here's what's in my Wikipedia bookmark:
Name: Wikipedia Quick Search
Location:
http://en.wikipedia.org/w/index.php?title=Search&search=%s
Keyword: wiki
Whatever is in the address bar after wiki will be inserted into the address at %s in the address.
so typing
"wiki Messenger Plus!"
in my location bar does a Wikipedia search and in Wikipedia's case, returns the best result.
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