Sometimes diving straight into a huge project is the best way to learn a new technology. (That's how I learned Visual Basic, ages ago.)

Sometimes a full, guided course is better, perhaps built around a textbook or tutorial -- especially if you're learning a whole new language.

But sometimes, when a new technology is similar but subtly different from something you already know; and when your goal is optimization as much as creation; a more problem-centered path of development can be best.

If you're thinking about WebGL development, and understand graphics a bit but worry about browser performance, then you might really benefit from Mike Cann's series of experiments (1,2,3,4,5) using HTML5 and WebGL with haXe.

His latest post caps months of spare-time labors with a pretty neat interactive demo of complex particle interaction, with source:

As a non-haXer, I found the project history helpful, especially Mike's careful work with stateless vs. state-preserving particles (starting with his third post).

Maybe take a moment to nod, impressed, at the (momentarily) final result, then trace the experiments all the way back to their (non-WebGL) original inspiration.