This is a pretty old feature apparently, but I just found out about it, and I think most people don't know about it, so I thought I would share the love. You can use the bookmarks "keyword" field as a method to create easy-to-type URLs. For example, for wordforge, you could make a bookmark with location: "www.wordforge.net" and keyword: "wf". Then, if you just type "wf" in your browser, you go to wordforge directly. This is probably something a lot of people knew about already, and really isn't that unsurpising by itself. What's much cooler is that you can set a parameter. Somewhere in your location, you insert "%s" (without quotes). This way, you can enter your keyword, a space, then another string, and the string will replace %s in your URL. So for example, lets say you use google products a lot. You could make a bookmark with location: "%s.google.com", and set the keyword to "g". Now, in your browser bar, all you have to type is "g mail" to go to "mail.google.com", or "g maps" to go to "maps.google.com". You can also easily set this up for searches. Any time you see a search box on a webpage, you can simply right-click it and select "add a keyword for this search". So you could go to wikipedia and add the keyword to be "wiki". Now, you just type "wiki elephants" in your browser bar if you wanted to see a wikipedia entry about elephants.
How do you get into the keyword field? I don't see it in the bookmarks menu, and right clicking on a specific bookmark doesn't have anything either.
Have to go to "organize bookmarks" and right click them from there, sadly. There is an addon you can get that allows you to set the keyword from any place you can modify a bookmark though.... I'll try to find what it is, I can't remember off the top of my head. edit: found it https://addons.mozilla.org/en-US/firefox/addon/42