If you're looking for a poor-man's version of a desktop sharing application look no further than Microsoft SharedView. It is a really nice, lightweight desktop sharing application that not only allows you to easily create a sharing session and invite participants, but it also allows you to turn over control to another user (but be careful with this, of course ).

You can download Microsoft SharedView here:

http://www.connect.microsoft.com/site/sitehome.aspx?SiteID=94