A few websites offer the following simple but (occasionally) useful service: you feed them a URL, long and incomprehensible, and through the wonders of modern technology they create a short and snappy URL which redirects to your original input, or possibly displays it as a (usually single) frame. This is sometimes handy if you really want something shorter to read out loud to someone, type in, or copy and paste, or perhaps to mildly obscure what page you're pointing to (especially in the non-redirecting case).
TenMinJoe says one big reason these are useful is that e-mails often auto-wrap things at approx 80 chars, so long URLs get broken en route if you mail them to people. TMJ's comment applies equally to various sloppier text editors, short input boxes/buffers, etc.
Two well-known sites which do this are w3t.org and TinyURL.com. The first has the advantage that you can ask it for a particular tag, so you get a URL you can read out loud or a reasonable mnemonic, rather than just a space-saving unreadable jumble. So, for instance, I gave w3t this http://www.everything2.com/index.pl?node=Everything%20New%20Nodes and got this http://w3t.org/?c=e2. That's all there is to it, really.