Although I'm sure for most TextExpander needs no introduction, in a nutshell, it allows you to expand short snippets of text into longer ones. In fact, this particular trick shows you just how powerful this truly can be.
You see, for a while I was using a similar snippet to the one linked to for shortening URLs with TinyURL. I would type /tinyurl and it would shorten. It was actually very cool. The problem is that TinyURL crapped out on me and hasn't been working at all for the past few weeks. Plus, although it was still far faster than doing it by hand, it was kind of slow.
This new snippet I found for doing it with j.mp is far faster, and, you know, actually works. Just follow the directions as to where and how to enter in your username and API key into the snippet and you should be good to go. It's really slick, and very useful, especially for places like Twitter.