What it is, is a customized search. To clarify, I'm not talking about the one that is just right of the location bar; I'm talking about adding "%s" to bookmark URLs, and then giving the Bookmark a keyword in the Bookmark Properties window. So then you can search using "keyword <whatever>" in the location bar, with "<whatever>" being the "%s" of the Bookmark URL).
Example of one I currently got:
Keyword: domain
URL: http://domainsatcost.ca/search.asp?sdomain=[b]%s[/b]
How I use it: "domain devnetwork"
Then that will bring up a domain search for the name devnetwork (com, net, org, ca, etc.).
Screenshots:


Hope this makes life easier. Sure did for me (as you can tell from all the ones I have so far--see 1st screenshot list of sites).