Hi everyone.
I'd just like to announce a new contrib which adds an easy to configure site-to-site VPN solution on SME Server. This contrib is called smeserver-openvpn-s2s, and, as the name suggests, is based on OpenVPN. It lets you connects several SME Servers, and their local networks, just as if they were directly connected.
Everything can be configured with a panel in the server-manager, so most of the time, you won't have to do any custom configuration by hands.
You can find more information about this contrib on the wiki:
http://wiki.contribs.org/OpenVPN_SiteToSiteRegards, Daniel