HSMM MESH Networks
Drop a battery powered package no bigger than a lunchbox and create a whole computer network? You can with the HSMM Mesh networks hams are developing.
What's a Trackuino?
Give a ham an an Arduino chip and they will come up with very interesting applications. Here's Kyle Crokett, KJ6KUV, with a hack named "Trackuino."
Visit a Maker Group
Justin Corwin runs "Radio Mondays" at Crash Space - a very successful maker group location. We visited him and caught some of the discussions there. You can learn more about them at http://blog.crashspace.org/
Teaching STEM topics
More schools are finding interesting "STEM" projects involving Amateur Radio. Here's one that powers their school radio with the sun and KI6WZB.
High flying ham
Alex Martin, KG6MOU, shows his gear for flying high altitude balloons and even has one up during a Maker Fair in California
Mini Satellites <$3k
Mike Safyan, KJ6MVL, shows his satellite. The hack is that the whole thing costs less than $3000