A lot of material on Albert Einstein, including the digital versions of his original manuscripts, can be found at the Einstein Archives Online website.
A nice introduction to ideas of general relativity in a comic-book form can be found in html version and pdf version.
A number of interesting articles about gravity has appeared in a special issue of the Science magazine, and can be found here.
In one episode, the MythBusters have tested one aspect of the weak equivalence principle, by demonstrating that the bullet fired from a gun falls to the ground at the same time as the bullet dropped vertically from the same height. The relevant part of the episode can be found on YouTube here. Their conclusion:
