goo.gl
Wikipedia lists these reasons for shortening a URL-- note that some sites will not allow posting of a shortened URL...
"Other uses of URL shortening are to "beautify" a link, track clicks or disguise the underlying address. Although disguising of the underlying address may be desired for legitimate business or personal reasons, it is open to abuse and for this reason, some URL shortening service providers have found themselves on spam blacklists, because of the use of their redirect services by sites trying to bypass those very same blacklists. Some websites prevent short, redirected URLs from being posted."
