Often in the line of IT it is necessary to troubleshoot on a user's computer. However, if you're lazy or the are multiple remote locations, a solution other than running to that user's computer is useful.
Currently, the highest ranked solution is Crossloop (free):
http://www.crossloop.com/ipage.htm?id=download
Another option is "LogMeIn" but it costs money.
Other options include VNC sessions, but these require having a VNC server installed on the local machine.
An upside to VNC sessions is that they can be recorded (.fbs) for future reference (liability):
http://www.wizhelp.com/flashlight-vnc/index.html
For the admin on the go, setting up a VNC client to view remote sessions is burdensome. Thus, allowing
VNC to be viewed from a web browser (java applet) is useful.
For me, UltraVNC server didn't allow connections ("framebuffer too large" after logging in). TightVNC worked.
Overall, web-based VNC sucks if the web browser window is small. There's significant lag-time.
Remote desktop isn't really an options, since it locks out the local user from seeing what's going
on and interacting.