If you'd like a three-letter domain, check out the lists below, showing domains that may be available. For domains that are already taken, there is a separate list. A .co domain makes an ideal short domain, so browse the list for your ideal short domain name.
Domain names containing numbers (digits) aren't included here, so you may want to search for those yourself. As of July 2010, they are pretty well available.
Please note that the links to available domains actually go through my 123-reg affiliate account; just search for the domain within your own domain manager if you prefer.