You site could use a lot of improvement for people with disabilitys and is not imho using the full power of the community. Right now here are IMHO a list of improvement I would like to see and the reasoning why IMHO I believe it would be an improvement.

1.)Add a button besides each video that allows downloading a Mp3(audio) button for those who can't read or see well a PDF(see) file for those who can read better
Reason:
While video most of the time will work well for people it not for everyone.
* There are some people who don't have high speed internet and can't view the content
*There some people needed to rewind frequently because they have a hard time comprehending. It very hard to get the video to the exact spot you need to be.
* It is proven you can read faster then speaking. This hurt people who are fast reader but have to re-read what they read frequently. You just can't do that in videos only.
2.) Add button to go to form besides each lesson for that lesson.
Reason: some people I believe don't even know about the forms and I believe it a hidden feature
3.) Add a type of wiki for each lesson Wikipedia I believe has proven that it is possible
4.)open source your learning platform or use an existing one.