Mozilla Firefox has dubbed their address bar the "AwesomeBar."
The AwesomeBar lets you use the URL field of your browser to do a keyword search of your history and bookmarks.
Firefox says "you no longer have to know the domain of the page you're looking for, the AwesomeBar will match what you're typing (even multiple words!) against the URLs, page titles, and tags in your bookmarks and history, returning results sorted by "frecency" (an algorithm combining frequency + recency).
Not only that, but the drop-list results show you the page's favicon, the full title, the URL, and whether you have bookmarked and/or tagged the page in a richly formatted two-line display."
The AwesomeBar was introduced in Firefox 3 and is still available in the last iteration (as of print, Firefox 8).
