Heroes, on NBC.com
Wikipedia

Based on the series Heroes. There were several web miniseries for this show, and I probably watched most of them (possibly all of them), but I don't remember anything specific about any of them. Anyway, you can't find any of them on NBC.com anymore, but you should be able to find them on YouTube or something.

Heroes: Going Postal
Heroes Wiki; IMDb

This was a series of 3 webisodes that streamed in 2008, between volumes 2 and 3 of the show.

Heroes: Destiny
IMDb

Four webisodes that streamed in 2008, during volume 3 of the show.

Heroes: The Recruit
IMDb

Five webisodes that streamed in 2008-09, between volumes 3 and 4 of the show.

Heroes: Hard Knox
IMDb

Four webisodes that streamed in 2008, between volumes 3 and 4 of the show.

Heroes: Nowhere Man
IMDb

Four webisodes that streamed in 2009, around the end of volume 4 of the show.

Heroes: Slow Burn
IMDb

Ten webisodes that streamed in 2009, during volume 5 of the show.