I was shocked that this wasn't posted before but Marble Hornets may be one of the best amateur web series I have seen.

The series is a horror series of ~48 episodes and growing. The series follows the crew of a student film called "Marble Hornets," but there is something that interrupts production.

The series is an expansion of the Slenderman mythos, which is pretty neat and interesting in and of itself. There are a few others in the same genre, like Twelve Tribes and two other really good ones, but Marble Hornets is the best.

Here is the first episode of the series. You can get the rest on the MarbleHornets account: