This has been suggested before. If the user doesn't sign up after they register and being emailed the link to confirm thier emaila address, then they either don't want to sign up, or they gave an incorrect email address. If they don't want to sign up, they will most likely not sign up when you email them again. If they gave an incorrect email address, your reminder email wouldn't reach them.
«------------------------------------------------------» Want to know when the next version comes out, as soon as possible? Join our Mailing Lists !
I was part of a company that did email validation as part of the registration process, and there were a lot of reasons that a person who wants to use your service missed the first incoming validation message.
Almost all commerical services send a reminder to you after some period of time.
If no one has code for this, then I'll put some code together for it.