Plugin for posting on top of a post?

I am looking for a function that I cannot find in WP.

The WP default is that you can post one article, and then viewer can add comment into it. Well I want to make it able to write additional post on an existing post. Maybe something like a sub-post, which would be featured as an independent post but yet it’s linked to the original post. For example, today I start an article about Barack Obama and post it, and tomorrow I want to be able to post another Obama article but somehow still ties back to my today’s Barack post. This will be useful if I post many different topics, for example I write about Barack, Hurricane, Gas Price, Foreclosure etc.

I am not too crazy in using tags. I know it helps categorizes your posts, but I want something more post-related. I want it when people click a headline on Barack, WP will show all articles about Barack that I’ve written, giving a feeling to the reader that all Barack post that I’ve done are closely related and acculumations of previous posts.

So maybe there is a plugin(s) that can help me achieve this?

Any idea is appreciated.