This video has been up for a few years, but was just recommended on the Open Culture site.
Now, we've all seen this type of illustration for General Relativity before on various science shows, but it is worth watching for a couple of phenomena that this teacher helps explain with his stretchy set up. Give it a few minutes and you will see:
I should also note that this month marks the 100th anniversary of Einstein's lectures on his theory. The New York Times gives a handy short history of how the theory subsequently progressed under the weight of 20th century politics.