The Idiot's Guide to Dance Music

Some clever sod has come up with this piece of website wisdom.
I've only had a cursory glance but it's crammed full of samples; select from a number of tunes per Genre or sub-category.
There's also a link to their streaming radio for each category, so you can listen in to your favourite music by Genre.
The home page has a nifty little tutorial on the history of Electronic music with sample sounds from the Theremin, Hammond B-3 and a couple of others.
Now all I need is for some cleverer sod to come up with a Rock version...