I just received a link to one of the most complete, interactive and interesting done presentation about electronic music.
The Ishkur’s Guide to Electronic Music.
As you can see in the picture (click for big) it represents all kind of genres and their links. Moreover, it´s all interactive flash, so you can even listen to several examples for each genre. More than 5 hours of music in total sum time! It´s really good work and a lot of fun. I think you can even call it E-Learning!