Firefox has a little-known feature called custom keywords – they’re sort of like macros with parameters for urls.
This is the only documentation I could find about it (there may be more functionality that’s not listed here):
Essentially, you can define a short string and use that instead of the full url, plus a substitution.
For example, if you wanted to search my blog, you could add a bookmark with the url “http://www.aquick.org/blog/index.php?s=%s&submit=Search” and a keyword “aquick”. Then, typing “aquick copying” in the address bar would give you all of the posts on copying.
Personally, I find this incredibly useful.