If you're using firefox, go to its address bar (where you type in URLs) and type "dict any-dictionary-word". You've probably guessed that this will take you to the dictionary definition of the word you typed.
Firefox comes with a bunch of predefined keywords such as this one (google, dict, quote, wp, slang). But you can also create new ones very easily. You can create an "lj" keyword so that you could type "lj lj-username" and go directly to the journal under that username.
I don't want to reinvent any wheels, so here's a complete explanation of the feature: http://johnbokma.com/firefox/keymarks-explained.html