Twitter announced its new approach to URLs today, explaining that they will wrap all links that spill over the character limit in their very own, new t.co shortener. What's really awesome about the new shortener, though, is that instead of showing a cryptic short link, it will show part of the original link so you know where you're headed (thus preventing spammers and phishing attacks).
Furthermore, the link will only count for 20 characters, the amount of text the actual t.co link takes up, instead of the length of the link preview (which is variable). The new shortener will roll out over the course of the winter. Hit the link for more information on the shortener and other features Twitter is integrating with it.