Hevx.info is a free url shortener service, much like tinyurl - it enables you to change a long url such as an ebay listing into a short url such as hevx.info/u/1234
It also comes with a build in twitter sharing link creater, so you can post your new link to all of your twitter buddies.
have a look and let me know what you think :
www.hevx.info
Thanks, Matt.