Think about a long-term project on which your class is currently working it could be from any academic area. Then extent that project to include a spacial activity. If you can,t think of something yourself, browse the teacher supply stores where you can find an endless cache of materials and ideas. And here's a tip: you don't necessarily need to bring your wallet just a pencil. some paper,and some spare time to scan materials you find useful. Then jot down ideas that will provide the basis for your special activity.