posted message: I posted a new example: GeoJSON in Leaflet.js https://p2pu.org/en/groups/online-maps-with-leaflet/content/geojson-in-leafletjs/
Also check out OSM Buildings, a Leaflet library to add buildings in HTML5 Canvas http://osmbuildings.org/
posted message: Looking for an afternoon Arduino activity? Check out Super Awesome Sylvia's YouTube tutorial: http://www.youtube.com/watch?v=3xCY2K9kQz4
Code for America 2012 Fellow and volunteer for One Laptop per Child (most recently in Haiti), formerly an ESRI mapping intern, participant in Knight-Mozilla News Learning Lab, and student at Carnegie Mellon University.
As someone without formal computer science or electrical engineering experience, I benefit a lot from open source projects on the web. Usually I work with HTML, CSS, and JavaScript. On the server side, I am a fan of Google App Engine, Python, and MongoDB to set up applications on a shoestring budget. For hardware - you can't beat Arduino.