Using a url shortener for marketing can keep the message to customers short and sweet. There is the advantage of easy tracking as a few of the services have analytics.
The list of url shorteners and recommendations are below.
Make Your Own URL Shortening Service - url shorteners - Lifehacker lifehacker.com — Make your own url shortening service. Lifehacker shows you how.
Google URL Shortener goo.gl — Google is new to the game but they too have a shortening service for url's.
A simple url shortener bit.ly — This is one of the more common url shortener services which integrates into other services / software.
YOURLS: Your Own URL Shortener yourls.org — Run your own url shortening service.
TinyURL.com - shorten that long URL into a tiny URL tinyurl.com — Tinyurl url shortener has something n. By clicking on the toolbar button, a TinyURL will be created for the page you are currently at.