For our eLearning project in our university, we are using Java applets to show some interactive stuff (like some interactive function plotting or some simple question/answer
If mobile access is important, the HTML + JavaScript option is really the only decent one you have, as it's the most widely-supported implementation technology across all of the Apple devices, Android devices, and many of the other mobile devices that support WebKit. (We implemented all of the interactivity on the Texas State homepage this way. http://www.txstate.edu/)
If you're OK with desktop-only delivery, Flash becomes pretty viable, Steve Jobs' protestations to the contrary aside. :) Some of our learning modules are built on that technology.