Someone mentioned unshort.me, but I created one a few months back for an internal project.

http://www.delinkify.com/

It has an API too, which is ridiculously simple:

    curl "http://www.delinkify.com/api/unravel/?links=http://on.wsj.com/aGFmsK,http://cl.ly/2ZY4"
    ["http:\/\/online.wsj.com\/article\/SB10001424052748703694204575518222145769804.html?mod=e2tw", "http:\/\/seldo.com\/weblog\/2010\/09\/27\/php_needs_to_die_what_will_replace_it"]

lately I've been annoyed by how Google's feeds often use their own feedproxy, so when I copy the link from within Reader, I end up with a link my friend can't use. (They never work for him.) And most of them have a forever-long url that they expand to, also. Some way to convert the url quickly and easily to it's final form, stripped of all the BS, would be welcome.

Sadly, this service isn't that.

You can get the original URL using http://unshort.me service.