Script Summary: Expands snipr, tinyurl.com, is.gd, zz.gd and bit.ly urls on Twitter and FriendFeed to show you where they're pointing.
Here's a list of a few that I could possibly add:
a2n, azqq, beam.to, b65.us, canurl, c-o.in, curio.us, cuturls, decent url, digbig, doiop, dn.vc, durl, dwarfurl, easyurl, ezurl, faceto.us, fly2.ws, get-url, hotredirect, hurl it, is.gd, just.as, x.se, linkslice, liteurl, lnk.in, memurl, metamark, minilien, moourl, myurl, nanoref, netshortcut, ne1.net, notlong, nutshellurl, oboeyasui, paulding, profile.to, quickurl, redirx, rubyurl, shim.net, shorl, shortenurl, shorterlink, shortio, short links, shorturl, shrot url, shorty, shoturl, shrinkr, shrinkurl, shurl, starturl, simurl, sitelutions, tighturl, tinirui, tinylink, traceurl, truncurl, tubeurl, turo.us, tweetl, twittu.ms, ulimit, urloa, urlbee, url.co.uk, urlcutter, urlcut, urlhawk, url.ie, urltea, u76.org, vdirect, wapurl, webalias, xil.in, yatuc, yep that url, zootit, 6url, 301url.
Oh and one more thing, you'll have to get a login and developer key at http://bit.ly/app/developers and enter it into the script to get it to work for bit.ly.
How it works: For every shortened link, I make an HTTP GET call to its respective URL expanding APIs. A more robust solution would be to grab the 30x redirect and not have to bother with any api, but this seems to not be working in FF. See http://greasemonkey.devjavu.com/ticket/107 for more details.