There are several sites that offer shortening of your URL’s. I started with Tinyurl and Snipurl about two years ago, but now use Budurl. The reason we want to shorten our URL’s is twofold. The first reason is for the convenience of having a shorter link to remember and to share with others. The second reason is to be able to track who clicks on your links and where they are coming from.
There is an excellent post about this topic here. It goes into much more detail than I have done here. Suffice it to say that it is extremely convenient to shorten your links. If you have a favorite post you can share it easily on Twitter. This also comes in handy when you are talking to someone. You just give them the shortened version and they can easily see what you are referring to online. I also love it for affiliate marketing. I use a shortener for an affiliate link, track the results, and then decide if I will purchase a domain for it or not.