For 90% of our clients, I use my own VPN account on their VPN/Router/Firewall box. Establish a connection and RDP from there. On the other 10% that don't have a VPN solution, half of them we have enabled RDP on their servers and set the firewall to accept incoming connections only from our IP's on that port. The other half of those, we just put them on our logmein account that we have. Currently we have something like 110 servers or workstations on the logmein account.
For personal stuff, I use logmein on my PC's and my familie's PC's to support them.
-d