Two ideas
Here are a couple of ideas that I won’t follow through will but would like to see.
First, a Digg-effectiveness calculator. It would randomly pick stories from the last two weeks or so and let the users vote in the style of The Funniest. Then it would compare the voter rating to the number of diggs received. Of course, the results would be more or less completely irrelevant, but I think it would be interresting to see which stories don’t fare so well even after getting thousands of diggs.
My other idea is a cliche detecting browser extension. Over at the Cliche Finder you can type in some text and it will highlight cliches. This extension would just be a right-click menu addition that does that same thing as the site.