Set up IPv6 Tunnel on VPS

I have a VPS with a single IPv4 and a single IPv6 address. I want to set up so that users who have v4 only ISP will be able to tunnel all their v6 traffic over it (just like tunnelbroker from [login to view URL]) This should be able to server multiple users from multiple IP address as a tunnel. you get full root on a fresh install of debain 6.0 (32bit) vps. Configuration on client side should be similar if not identical to that ones that HE offers... Summery, I want a vps to be set up just like HE's tunnelbroker servers.