Twitter requires you to write within 140 characters (and no more) so it's important to shorten any URL you want to include in your update. TinyURL and bit.ly are fine and do what they should - but Ow.ly helps you extend your network reach more than both of the others.
Try this...
Now go to Ow.ly and enter the longer URL (same one you used initially in TinyURL) and click "Shrink it". Then copy the shortened URL and add it to your Twitter update.
The difference is that Ow.ly helps you extend your social network reach more than TinyURL. Click the shortened Ow.ly URL. It not only takes you where it should - but it also allows the reader to:
(1) extend your link (or whatever was on the URL page)
(2) reTweet your Tweet (confused?)
(3) share your Tweet to other social networks (through www.gigya.com)
(4) or rate your Tweet
You can also shorten the URL and immediately use AddThis to push to any number of social networking venues.
