If you tweet or blog, you will usually link to other online resources. Some of those resources possess ridiculously long URLS composed of apparently random alphanumeric strings. Bit.ly (the .ly part is Libya's national web identifier, but one trusts bit.ly's servers are not located in that currently troubled locale) is a URL shortening service. You paste in your unwieldy URL and they give you a much shorter version, ideal for saving space in tweets. If you sign up with them (free), then you can customise the new link a bit to make it more memorable. The end user will click on the shortened link and bit.ly will automatically redirect them to the actual destination. Bit.ly may not last forever, but it should stick around long enough to provide a useful service to content creators on the Interweb.