CNET'S QUICK GUIDE: HDMI and HDMI cables

HDMI.org's FAQ
Source: HDMI Licensing, LLC.
Our take: This is the official FAQ of the HDMI Licensing organization, and includes some of the more technical details about HDMI. Some good content, but aware of some spin on topics like HDCP and HDMI's advantages over component video.

The Ins and Outs of HDMI
Source: CrutchfieldAdvisors.com
Our take: Another useful guide to HDMI, if you're still looking for more information.

Wikipedia: HDMI
Source: Anonymous contributors
Our take: Like much of Wikipedia, there is a lot of good info, but it's extremely technical and loaded with jargon. If you want to know what each of the 19 pins on an HDMI connector does, this is your guide.