I didn't post this lesson example as soon as I anticipated, obviously, but better late than never, right??!!
My students completed the eCybermission project in March of this year. Sponsored by the US Army, it's a problem-finding and -solving competition which requires students to use the scientific method and science, technology, engineering, and/or math concepts to identify and propose solutions to community problems.
My students covered many different issues, from excessive cafeteria waste to acne-causing bacteria, and many were surprised by the solutions they found, not to mention the creativity they didn't realize they possessed. This project would be perfect in a mixed-ability classroom because of the huge diversity of opportunities and challenges it offers, especially since it places such emphasis on teamwork.
The unit plan I wrote is here.
And one of my groups was a winner :)