The oldest still registred domain that hosts a website is that of BBN.com, acording to a list of the 100 oldest domains. BBN is actually the second oldest domain, but Symbolics.com doesn’t appear to have a website.
BBN essentially built the internet, but chances are you haven’t heard of them. Now you can find out all the neat little facts for which I shelled out for a history of the internet book. And think of Ray Tomlinson next time you send an email.