GoToAssist is too expensive. Over 300 per month and for an independent consultant thats a lot. WebEx is also not cheap. I use 2 methods. I use EBLVD for remote support mostly. (http://www.eblvd.com) They charge $89 for a rotating 50 PC's. In other words you can have 50 setup at the same time and if you need another just delete some to make room. I works like Webex and GoTo as it runs through a data center with 128bit encryption. It also runs on port 80 and is seen as originating inside on the client so there are no issues with firewalls. You have the client go to a long URL they can get from an email. An active -x control is then installed that starts a small host install. The down side is this requires admin access for the install. Then you can connect to any client from any browser. I told them 50 was more than I wanted and they cut it in half to 25 pc's for less money.
What I do is install VNC server in the office on the workstations. I use the secure eblvd to connect to a server and then use VNC viewer to connect to any client. Works great. I do use eblvd direct to some workstations. I also use VNC from a remote site sometimes if I have a vpn setup. I try to avoid VNC remote if I need to open a firewall because it is less secure in it's free version.
Good Luck,
razz