Firefox only (Windows/Mac/Linux): Firefox extension Long URL Please changes almost all shortened links in a page back to the real URL—so you can easily see where a link is really taking you.
Using the extension is simple—by default all URLs and link text are simply replaced inline but the text is truncated to not break the page layout. Long URL Please works with the majority of your favourite URL shrinkers, so you can hover your mouse over the link to see the real location for almost any link. The options panel allows you to change this feature to only replace the URL, replace the entire link, or any combination that you want—it's a very useful extension that is worth a look for anybody tired of not knowing where a shortened link is really to.
Long URL Please is a free download, works wherever Firefox does. Alternatively, you can use the previously mentioned TinyURL Decoder to display the real address behind TinyURL links—though it doesn't work for all of your favourite URL shrinkers.
Long URL Please [Mozilla Add-ons]