I couldn't find a post with these blogs as the main topic, so if there is one, sorry!
I found this series through some of the followers on my own blog, and I've been following it for the past few weeks. I'm mad at myself for not watching it sooner, but it's still a great read in my personal opinion. I definitely recommend them. Alder's the writer of these blogs, and I believe he's been working on a "How to write a good story" thread.
The first blog follows a few viewpoints, but the main protagonist is a guy named Peter. He's been running for about eight months since the blog's start, and at one point he met up with a group of runners who are trying to survive in a world where they're being hunted by an eldritch abomination. The story follows them trying to find a safe place - if there is one.
One of the things I find fascinating about the blog is the character interactions. When I was reading it, they felt genuine, like actual people whom you could relate to. The characters' relationships with each other also feel real to me, and I couldn't help but feel for them when something went wrong for their group.
I don't want to talk about the second blog much because it'd spoil the first blog for you, but it's currently going on right now. It features Kari, a character of Alder's whose blog ended about a year ago, and will likely feature another character who may have information regarding the Slender Man... If anyone's read "Old Celluloid" (another of Alder's blogs, as a matter of fact), you'll recognize the name.
You could just look at Alder's signature to get the links, but since I'm such a jerk I'll provide them for you.
Be sure to check out some of Alder's other stuff, too! He's a great writer, and I'm definitely going to spend time looking at the rest of his blogs.