I use DNS2Go from Deerfield software... When I first signed up, it was free... Then they moved to a fee-based model. It is $19.95 a year for one domain, 6 Domains for $29.95, and up to 12 Domains for $49.95 per year. This does not cover the domain registration, it is just the redirection service.
http://dns2go.com/
It runs as a windows service on my server. So it starts when the computer is turned on and nobody is logged in.
Though it is not free, I like it!