This addon allows you to type searches directly into the URL bar, like:

g Songbird Addons

will be transformed into: http://www.google.com/search?q=Songbird+Addons, which will perform a search for the terms “Songbird Addons” on Google.

Of course you can supply your own Search Engines from anywhere around the Internet with your own IDs and of course you can supply as many as you like. (Although this might not fully be true since it is probably limited by your system memory/harddrive space and some of Songbird’s internal memory and storage settings, but I don’t think that you will exceed that…)

Another pretty nice feature is that you can also input any Javascript etc. instead of a normal URL, so – with the necessary knowledge – you could also build yourself a mult-search that opens up, lets say, Google, Yahoo and Youtube with the same search term.
Or you use it for something totally different, like a script that changes the background color of the current site to a different value (whatever that might be useful for…).
Or something else – be creative!