Both brian and I were scheduled to do the first talk of YAPC on Conferences for Beginners. Unfortunately, due to some travel problems, brian wasn't back to his home city of Chicago in time.
So on a moments notice, the Perl hackers took the stage and got things started. Then, using a borrowed video camera at the conference hall, Randal and I got a video iChat going. Randal had his display on the big screen and his audio going through the PA, so I was able to give the presentation from home.
Not quite the same as being there, but an excellent way to solve the problem.