Many to many VPN

If you have servers in multiple countries and people using those servers in multiple locations what's a good way of setting up a VPN? If you have a VPN server at each DC then performance will be great but users have to setup multiple instances of the VPN software which they will mess up and time will be wasted. If you have a VPN server at one DC then a user who connects to a server in a different DC gets longer ping times. Also an outage in one DC breaks everything. Any ideas? Support is required for Linux servers and Linux, Windows, and OS/X clients. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/