[ctviggen]

This article is a good introduction to class D amplifiers:

http://www.audiodesignline.com/showArticle.jhtml;jsessionid=VDT55SVPDUAXUQSNDLOSKH0CJUNN2JVN?articleID=177102531

Actually, the main site has a ton of info regarding various aspects of audio:

http://www.audiodesignline.com/

The "tech library" isn't so great, but there are quite a few articles available using the search function.

[ctviggen]

Yikes!  According to this article, the power supply rejection ratio for a class D amplifier is zero decibels.  Is that true for most class D amps?  If so, that means you really need some AC filtering, at least in the audio band. 

[tranh]

That is true.  That why a very stiff power supply is necessary in open-loop classD designs such as former Apogee's, or TI's pure digital audio IC.  Robust systems always have feedback.