A software package a day: GoToMeeting
There are a lot of solutions for sharing desktops these days, some are even free (such as using one of the various VNC tools) or built in (such a Remote Desktop is). For my mix of uses (which include both small groups for trainings or demos and one on one technical support) I find GoToMeeting a good mix of features and price point. Perhaps my favorite feature is the ability to have people dial into the meetings either via a standard phone number or built in a VoIP feature at no additional cost (standard long distance fees apply for the phone number for the callers).
There isn’t much to say about the software if you are familiar with other meeting software. All of the basics are there: sharing the entire desktop, individual monitors (useful for dual or better setups) or even individual windows (the best if you are concerned about accidental information disclosure). Mouse and keyboard control can be handed off which makes it double as a technical support tool. Just have them visit http://joingotomeeting.com, install the application and enter your meeting ID.
There are other solutions out there that are less expensive but they either lack features (only operate one on one, don’t have a conference number, don’t have client desktop viewing and control, etc…) or have failed to operate through some firewalls. Recommended.