Personal version of LogMeIn.com

Just wondering if anyone has heard of those Remote Control companies
like GoToMyPC.com or LogMeIn.com. I like their methodology in that
both client and server sides access a central server giving the
advantage of not having to open ports for either the client or server
and can circumvent most corporate firewalls. Does any one know a
software package that I can put this "central server" functionality on
a personal machine and mimic their service for my own uses?

Thanks.