Notes and Domino 8.0.1 contains new policy settings for controlling user access to update sites and the documentation is pretty decent on the specifics. See the topics below in the Domino 8.0.1 Administrator Help information center at http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/index.jsp.
Controlling feature install and update with update sites
Specifying available update sites (and its several task-based subtopics)
There is also great information in the developerWorks blogs, such as NSF based Update Sites.