What makes a great case study (ie. one that's likely to get your website featured here)? Here are a few tips. You certainly don't have to follow them all, but they'll give you an idea of what I'm looking for.
1) A great case study reveals a solution to a common problem: how to improve one's search engine rank, how to get more traffic, how to make your site "stickier" (keep people on it longer and get them to come back later), how to do a common thing better than it's commonly done, how to make something easier (or something that seemed impossible possible), etc.
2) A great case study suggests new things to try and new areas to explore rather than just little tweaks to old ideas. This could include examples that show how to use a feature that many people don't know how to use or have never considered, even if the feature isn't being used in a revolutionary way -- as long as it's shedding light where there was darkness, and what's revealed by the light is worth implementing.
3) A great case study includes specific results: "After I did this, my traffic increased by 2 1/2 times", "I got over 30 emails telling me how much my subscribers liked the new feature", etc.)
4) Especially if implementing the solution covered by the case study requires code that the average user couldn't easily recreate, a great case study includes code.
5) A great case study isn't so long that no one will read it.
6) A great case study focuses on one issue/problem/solution. That doesn't mean that it has to focus on only one webpage or feature, but if it covers multiple things that were done or multiple pages, the "story" should have a clear unifying theme.
I'm really looking forward to showing off your websites so that you can be inspired by each others' ideas and find new ways to make the most of the software I'm developing for you. If you have a site that everyone should see, contact me through my case study information submission form.
And if there are things you'd like to see in case studies that I didn't mention here, please post them in the comments.