Heroku and GoDaddy CNAME
If you're trying to get Heroku working with your GoDaddy-hosted DNS, you're going to have problems adding a CNAME record for "@". The system will complain and ask for a valid hostname, even though GoDaddy's own documentation says that "@" is okay.
The solution is to use the name of your domain instead. A trailing period after the TLD seems to be optional. An A record for @ is not needed with this configuration.