You could just create a PPTP connection from a single client to your server.
It is possible to setup an IPSec (FreeS/WAN) VPN between a static IP and a dynamic IP per a post here by Todd Pearsall in June. You set up the static server to listen for connections, and have to start it from the dynamic end. I'm not sure if it's possible to set things up to support both ends being dynamic though...