Remote Assistance

Does anyone know of any kind of remote assistance software that would be userful when troubleshooting with a user that is not on the same network as me. I know of the netmeeting, remote desktop, and remote assistance. With all of the listed titles, it seems that they will not allow me to connect to a users’ workstation with me not being on the same network. If anyone has any suggestions for me, I would greatly appreciate it. Thanks