I love stats, I really like to take them apart to see what did what and what didn’t. I also love twitter.
Now, if you can put stats and twitter together then I’m drooling.

Here’s 6 ways I have found to track the links that I post on Twitter.

Install Get-Shorty

Getshorty is a beta script available that allows you to install your own personal tiny url service to your server. It allows you to use keywords as part of the url or let it automatically create one for you.
Site: Get-shorty

Create your own URL shortener with WP 2.7

This is an excellent way to completely control how your links look and where they point to. It takes a little work and some template changes but combine it with some decent stats tracking and you will have a full service all to yourself!
More info: Business Mind Hacks

Google Analytics

If you have Google Analytics on your page you can add some variables to the end of the your URL so google can store some extra information about the visitor.
Example:
http://www.you.com/?utm_campaign=promotion&utm_source=twitter&tm_medium=social
You will still need to use a URL shortener such as tinyurl or one of the others that don’t provide tracking services.
More info: Epikone

Use Tweetburner

You can use tweetburner to shorten a url for you and track how it performs over time. The advantage of this is that the twurl.nl links are integrated into desktop programs such as twhirl and tweetdeck.
Site: Tweetburner

Use Budurl

This is another URL shortening service with added support for link tracking. Their dashboard for tracking your links is quite extensive and a dream for stats geeks.
site: Budurl

Use bit.ly

This is my favourite URL shortener service. It’s integrated with tweetdeck and the stats page is very useful. You can even watch results in real time as people click your links. You can look at the stats on any bit.ly link by entering it into the search box or if you register and provide your twitter username, you can bring up all the bit.ly links you have used in your tweets and see how many clicks have happened over time.
Site: bit.ly
(you can see the results of this post being retweeted by @styletime on this link here)

You don’t have to have twitter to use these tools, they’ll work perfectly well for affiliate links and flyer links. I’d recommend going with the self hosted option if you post a lot of links on forums or other places where they stay a long time so you can be sure they wont expire or if you need to update where it points to.