The canvas element in HTML5 is exciting because it really opens the doors to games, drawing, and animation. This is especially exciting as browsers hardware accelerate canvas and improve its performance. What isn't so exciting though is that you do have to do a lot more for yourself.
Most of the time, installing things with MacPorts is pretty easy; however, I have found that GNU Octave can be a little tricky. That being said, it's still pretty easy to get Octave up and running in both Snow Leopard and Lion.
I'm starting to use the closure library and all of it. The closure compiler is nice because it can compress your JS code down, a LOT. In order to get the biggest bang for your buck. you want to use the advanced optimization settings. It can eliminate unused code, inline functions, and rename variables.