LogMeIn is a web-based remote access program which is clever enough to find its way around firewalls. Much like Windows remote desktop sharing, you can send an eMail to a person with a web link, and when they click on the link, it installs a tiny program on their workstation which allows you to perform maintenance or offer support to the user. LogMeIn is available in several versions, from free, for remote support, to the most comprehensive version LogMeIn IT Reach which gives access to several server and system functions on the target PC.
LogMeIn IT Reach is sold as a software service, per month at $12.95/month. Their Pro version, which might be ideal for supporting end users, is priced per technician…who can then support any number of workstations.
There is a review at PC Magazine.