I don't believe for a second that ALL one word domains are taken. Surely there are some relics out there that haven't been discovered yet?
Anyway, if (by some miracle) that is the case, check out the internet forums. There are some people on there who don't realise how much their domain is actually worth and therefore sell it really cheap. Take 'Vibrators.com' for example - a company paid a million dollars for that, but if it'd sold on a forum it would have gone for a couple of thousand dollars AT THE VERY MOST. ;p