If a Twitter username has been idle for (6? 9?) months, you can request that Twitter let you take it over. However please note that these are considered "low priority" requests and can take a LONG time for anyone to respond.
And this list isn't the place to do it. http://help.twitter.com/portal is probably the right place to start. I'd recommend finding another name for the time being. TjL ps - with all the "one post wonders" out there, I hope that Twitter will eventually go through and purge accounts that haven't been used in a year.