It's pretty clean cut and to the point. I like it.

One thing that you could change is, after you click the "spit!" button and convert the url, it's kind of difficult to spot the new url at a glance. So, you should make the text "Your SpitUrl is: http://spiturl.com/h" a little bit bigger I think. And maybe even get rid of the example text if some one has already submitted a url to be shortened; it's just more info for the user to parse through to find what they're looking for -- their url.

Cool stuff.

People are actually starting to use this site.
There is 344 results on google for "spiturl.com"
But alot of the people are using to spam digg and reddit

Haha, very creative name for sure. My spitURL is number 2!

http://spiturl.com/2

<div id="addressbox">
      <small>Submitting this form constitutes acceptance of our <a href="http://img.spiturl.com/tos.php"><b>Terms of Service</b></a></small>
      <form action="http://www.spiturl.com/index.php" method="post">
     
         <fieldset>
            <label for="longurl">Enter a long URL:</label>
            <input name="longurl" id="longurl" type="text">
            <input name="submit" id="submit" value="Spit!" type="submit">
         </fieldset>

     
      </form>
     
</div>

a good one.
Out of 5 , I would give it 4.3.
More tags needs to be added.