Where is the software that enables the long tail?

For a product to reach the long tail, it has to have three things.
First, it has to have a low barrier of entry. Anyone needs to be able to create content and publish it. Second, it has to be easy to access. This means it must be searchable. Finally, it has to allow others to review and comment. That's it. It's not rocket science.

Unfortunately, I'm having tremendous trouble finding software to enable the long tail. I really don't have overly strict requirements. In application 1, I want to be able to allow people to post Java jar files. I might want to check things on post, such as does it have a MANIFEST? In application 2, I have a site where I am putting up papers about record linkage. I want others to be able to post links and have the software verify that the links exist. In each application, I'd like to also allow them to associate a title with either the jar file or the link.

For search, I want application 1 to be able to search the javadocs that I generate from the source in the jar files. In application 2, I would love to have the content of the links searchable (so that people can find which PDFs contain information about blocking), but I'd settle for just being able to search the title that was given to the link.

For ratings/reviews I would like to have a 5-star rating system and comments. However, I'd settle for just the comments. I want people to say which papers they found readable or which jar files they found useful.

There are a lot of features you could add such as an RSS feed, etc..., but I'm willing to ignore all of that for right now. I just need the basics.

Am I asking for too much? Why doesn't this already exist? In the world of CPAN, reddit, etc... why doesn't a generic version of long tail software exist? Perhaps I'm just overlooking it. If not, I guess I'll just have to write it, but I'd much rather use something already written.

Let me know if I missed something!