URL Shortening service makes long URLs short and easy to pass along. It is very convenient for micro-blogs like Twitter and identi.ca because of their 140 characters limit and it is more useful to send short URL in emails or in newsletter. You can find here The top 10 Shortening URL Services. Bit.ly is one of the most used in the cloud, it comes with TweetDeck, TwitterFeed and other tools for Twitter.
URL shorteners can be blocked by your office’s firewall because nobody really knows what’s on the other end of that link until you click on it. With Short URL, you can not analyze the link and get its source except if you make a reverse Short URL lookup using other Long URL Tools like LongURL or ExpandmyURL.
You may find this list of Top 10 Websites to Expand Any Short URL useful. All these tools are useful for a single URL but it is hard to analyze a long list of URLs at once.