Yes, this is in Firefox too. I've had `wp %s` bookmark for many years now bound to the wikipedia search page, so I do `wp cat`, etc. etc. The JavaScript example really didn't hit home for me either because I'm always on Freenode, and /msg ecmabot mdn [term] is faster than anything else, especially because I usually have a chat open with ecmabot already.
And in Firefox, you can either set it up in the search bar's menu (by going to its preferences), or, if there is no search plugin for a site, go to that site, right click in the search box, and choose "Add Keyword Search". This'll create a bookmark with the same effect.
I've done this for every single site I search regularly, and have used up almost all 26 letters at this point. It's amazingly useful.
