I think it would be really cool if Mojo implemented a module that allowed easy setup of sites like Digg/reddit/slashdot. So, you'd basically have a system where users could submit links to relevant articles, which would place them in an "Upcoming Articles" section. The articles could then be rated by users. Once the article received enough points, it could be placed on the main article page to be up and downvoted. Comments could be placed on each article submitted as well, getting an up or down vote. The user would get points based on the ratings of the articles and comments they submitted. It would also be very cool if you could do the same thing that DotNetKicks does and allow users who post articles to get revenue sharing via google adsense.

For reference, check out DotNetKicks.com, as it is open source and .NET based.