1. A learning system for providing an interactive, educational lecture, comprising: a plurality of computing devices, each of which is in communication with the same distributed computer network, and at least one of which is located at a site where a presenter of the lecture is located and each remote location participating in the lecture; equipment sets for capturing audio and video (A/V) at the presenter's site and remotes sites, and providing it via a computing device resident at the site to the network, wherein one of the A/V equipment sets is resident at the presenter's site and wherein other ones of the A/V equipment sets are respectively resident in at least some of the remote sites; and wherein the computing device in communication with the A/V equipment set resident at the presenter's site further comprises a A/V computer program having program modules executable by the computing device, wherein the computing device is directed by the program modules of the A/V computer program to, multicast A/V data captured by the A/V equipment set resident at the presenter's site over the network; subscribe to A/V data multicast from remote sites via the network, and render and play the A/V data received over the network from the remote sites; and wherein one of (i) the computing device in communication with the A/V equipment set resident at the presenter's site, or (ii) another one of said computing devices also resident at the presenter's site, further comprises a slideshow computer program having program modules executable by the computing device for directing the computing device to broadcast presentation slide data associated with the lecture over the network; and wherein the computing device resident at each remote location further comprises a computer program having program modules executable by the computing device, wherein the computing device is directed by the program modules of the remote location's computing device computer program to multicast a still thumbnail image separately from the A/V data to the presenter's site and the other remote locations via the network, wherein said thumbnail image is representative of the remote location, and wherein each thumbnail image received at a remote location is displayed separately from said A/V data and presentation slide data.