Twitter’s 140 character per-post limitation created a whole new segment of web services called URL shortening. If you are not familiar with these services, they basically create a 12 character URL for any long URL that you provide it. An example of a short URL is http://www.bit.ly/abMsaC. Ironically the URL is provided could actually be shorter because most web browsers today do not require the http:// or the www portions at the beginning of the URL.
Using a service like bit.ly to create short URLs is very easy on a desktop PC, but it can be more difficult on mobile phones. Most mobile Twitter clients will automatically shorten URLs, but if you have a client for Windows Mobile that does not then you can use ShortenMobile. The program works very simply by monitoring any URL that appears in the clipboard, automatically creates the short URL, and puts it in the clipboard in place of the long URL. Keep in mind the application has to be continually running on your phone to work, and that can take up program memory. However, if there is plenty of memory on your phone and you use Twitter a lot, the program may be worth running.