I saw an article about a mini quadcopter that uses an ATMega128RFA1 (8 bit processor with built in 2.4 GHz transceiver). It's pretty cool, though the website didn't have a lot of build information in the post (there's some more stuff in his earlier posts, but it's not a clear cut thing to look at and know how to build your own without previous knowledge. Maybe I didn't look long enough.) Good instructions or not, it's a sweet project.
Speaking of Quadrotor helicopters, there's a nice youtube series done by The Crash Cast about building a tricopter (three rotor helicopter). If I ever have time to build one, after all of my other projects, then this is where I'd start. Maybe after I'm done teaching about registers and bits I can start teaching about PID controllers with this. How cool would of an advanced project would a quadcopter helicopter be (or tricopter. I don't judge)?
Adafruit has a tutorial on building a Magstripe reader to parse the data off of a credit card or other such magnetic strip.
I ran across the idea of recording my lessons via iPad using this tutorial (I probably want to have objects to demonstrate with, so I may want to not use an iPad). I was inspired by Salman Khan of Khan Academy (great article here about him). I can create the non-linear curriculum that I want by making the lessons cover everything that you need to know while putting links in the video to point people who want to learn more to more things (hence non-linear learning. There are many branches that you can go down in addition to learning the core material).
The whole point of non-linear learning is to capture the moment of inspiration, that time when someone is genuinely interested in a subject and wants to learn more. It is at that moment that I want to present the possibility of diving into extra material that goes above and beyond what is necessary to understand what I want people to learn. I've always wanted a course that gave me the opportunity to learn more than was necessary and explore things that I found interesting, and now I can create that for other people.