URL shortening sites have become popular with Twitter users, ever mindful of the 140-character limit, as a way to avoid pasting long, unwieldy URLs. Copy a link, paste it, click, and you've got a URL to share with your Twitter followers. A URL shortener is a simple, no-frills tool.Now, though, URL shortening services are drawing a new crowd of users who aren't necessarily interested in just saving space on Twitter\u2014users including bloggers curious about who's linking to their sites and businesses interested in tracking the ROI of social media efforts. A number of URL shortening sites have added or are adding new features ranging from detailed analytics about who's clicking your links and geographically where they're coming from, to features that "unmask" shortened URLs\u2014so you know where a link will bring you before you click. The tools also provide easier ways to shorten and tweet, without leaving the webpage you're viewing.Here are my top three picks for URL shortening services that do more than save space. \n\nBit.ly\nSidebar Bookmarklet: This browser add-on gives you quick access to shorten URLs; shows you personalized stats for your bit.ly links (such as how many people have clicked on a link); lets you Tweet directly from the sidebar without leaving the page you're on; and shows you in real-time who else is talking about this page on Twitter, FriendFeed and blog comments.\nBrowser Extensions: Bit.ly also has browser extensions for Firefox and Chrome that expands bit.ly and many other short links so you can see to which site you'll be brought before clicking.\nAccess Link Data Generated Outside of Bit.ly: Twitter clients Tweetdeck, Twitterfeed and Seesmic let you enter your API Key so you can get personalized tracking data such as click totals and other information about you links. For more information on how to do this, click here.[Concerned about the security risks associated with shortened URLs? Read recent coverage here.]\n\nCli.gs\nGeotargeted Destination URLs: One unique Cligs feature is what the site calls "Right Cligs"\u2014the ability to create alternative URLs based on a visitor's country by creating "rules" that tell Cligs, for example, that if the visitor is from the U.K., send them to a different URL instead. You can view a short tutorial about geotargeted desitnations here.\nReal-Time Analytics: Cligs keeps track of the following: hits time, i.e. when your traffic came in; geographical location of your visitors; search engine bots, i.e. which sites have found your links; Twitter and FriendFeed mentions; blog links and comments; Web links; del.icio.us saves and referral statistics.\nTools: Additional Cligs tools include: a Wordpress plugin that automatically posts your Wordpress blog posts to Twitter when you publish them; a bookmarklet that lets you shorten a URL and\/or post to Twitter; a Firefox extension; and an iGoogle gadget that lets you create shortened URLs right from iGoogle or Gmail without leaving the site. \n\nIdek.net\nBookmarks: Idek has a bookmark tool that makes shortening URLs on the fly a lot easier. By visiting this page, you can drag and drop a link to your browser toolbar. When you visit a page with a long URL that you'd like to make shorter, you click the Idek.net link, which automatically grabs the URL and the title of the page and lets you write up a few words about the link, then sends the tweet instantly to your Twitter account.\nMetrics: For every URL you create with Idek.net, the site tracks a number of metrics, including: total number of clicks; clicks per minute\/hour\/day; clicks per hour of day; clicks by day of week; number of tweets; number of tweets of the URL translated to other popular shortening services; and more. To view the metrics for any Idek.net URL, add \/s to the shortened link. You can find sample metrics here.\nOther Features: Idek has a plugin for Wordpress and plays nicely with 301 redirects. It also has an open API soyou can tweet directly from Idek.\nStaff Writer Kristin Burnham covers consumer Web and social technologies for CIO.com. She writes frequently on Twitter, Facebook, LinkedIn and Google. You can follow her on Twitter: @kmburnham.