Reputation and filtering

[mykes]

I've spent a bit of time searching through the site and available mods, but the only thing close to what I am looking for is in the graveyard.

I have a fairly large and active forum and I don't want to enforce a lot of rules on the posters. My theory is that it's better to figure out ways to promote great content and demote the garbage content, and the ideal solution is something along the lines of reputation and thread ratings. If the community is encouraged to rep the good posts and negative rep the bad posts, rate the threads as well, then filters could be applied that show threads with a high enough rating or posts with a good enough rating.

Something like what slashdot does.

I particularly want only the best content shown to first-time guests.

Is there a mod or built-in feature I've missed?