Well, I can save you some money: there are virtually no personally identified IP addresses anymore. A simple Google search can find you an IP tracer, but it’s pretty likely you’ll get “AOL” or something similar. They haven’t identified people personally in years.
If you’re asking about a person commenting on http://cliffavant.com/, that’s a private blog and presumably all the commenters are known to the blog owner. You could just ask them, if that’s not you.
As for email addresses, you’ll probably have to subpoena the email host.