Another tool that I had used before but was reminded of at the conference today was Prezi. This was my initial attempts at building a map of physics. You can click through it one step at a time (linearly) if you'd like, but you may also zoom out and then click on a particular concept and it zooms in to that point of the conference. I think one of the best uses for prezi (although probably not yet fully realized) is the ability to create something that is both linear, and not at the same time.
By the way, you can embed pictures, videos, or text into prezi's. Perhaps other web2.0 tools too like polleverywheres or answergardens?