I am ready to register a domain name, however, as I have not yet built my site, I have not decided on a web host. Does anyone have a suggestion for a good place to register a domain name that is not only reputable, but also allows for an easy and cost effective transfer to another web host once I am ready to publish my site?

You don't need to "transfer" to another web host. When you are ready to web publish, just sign up with a web hosting company, and point your nameservers to theirs. Shouldn't cost you anything just for that.

Thanks for the info. Any suggestions on a good place to register a domain name?

http://www.godaddy.com that's the place you can book your domain.

And as nameslave suggested, book your domain with a reputable registrar and use the name servers provided by your selected host to point your domain to their server, this way your domain name is safe, any time you need to change hosts you just have to change the name servers to the new one.