Take  a look at 3 Twitter tools that are used my most of the Twitterers:

Bit.ly

Bit.ly is not just a URL Shortening service site but it also gives you access to create your custom short URL. Besides, you can share, track or analyze your links.

SocialOomph

SocialOomph offers wide range of services with just a free account. You can schedule tweets, track keywords, extend your Twitter profile, and much more.

Tweetdeck

Tweetdeck is desktop management twitter tool that allows you to create columns to organize your twitter daily tasks and use their interface Deck.ly that automates shortening URL.