Excerpt from article primarily about STEM subjects, but it will stimulate your thinking:

If you need a jumping-off point, take a look at the National Academy of Engineering Grand Challenges. These challenges are divided into four major themes: sustainability, health, security, and joy of living. Some of the challenges that might inspire middle-school students revolve around solar energy, clean water, health care (including food shortage, disease, and accessibility), and urban infrastructure (including transportation systems and municipal structures).

• Take a stop at the Boston Museum of Science for comprehensive and well-designed engineering curriculum targeting all age groups. The museum’s Engineering Everywhere Curriculum Units offer free STEM lessons that focus on unique and interesting real-world challenges. For additional ideas, check out these 20 hands-on Engineering is Elementary Curriculum Units.

• You can find a wide variety of STEM lessons and activities geared to specific grade levels at eGIF Dream Up the Future.

• Another one of my favorite sites is PBS’s Design Squad. You can find intriguing problem-solving ideas in the activities and lesson plans sections.

• The Teach Engineering site also offers a number of STEM/engineering lessons—be sure to browse these Maker Challenges.

• For high-school teachers, an excellent resource is Rutgers Today, which describes more advanced real-world problems. High school students in upper-level math or science courses might be able to design and implement solutions for these types of problems.

Source - Education Week