Ok, so I have an account with hostmonster that I host all my sites on. I registered all my domains through godaddy. Lets say I wanted to sell one of my sites. How would I go about transferring it to the buyer without disrupting any of my other sites?
There are variations, but you could send a copy of the website content to the buyer and push the domain name to his Godaddy account. He would create a hosting account with service he uses and then change the DNS to point to his server. Sometimes sellers allow the buyer access to their hosting account to copy and move the content themselves.
The best way is to push domain to his GoDaddy account and give him all files and databases needed to run this site.