Found this on AVS forum. I know this has been discussed before in various different threads, but I thought it would be good to have it all in one place.

HDMI 1.0

Released December 2002.

* Single-cable digital audio/video connection with a maximum bitrate of 4.9Gbps. Supports up to 165Mpixels/sec video (1080p60Hz or UXGA) and 8-channel/192kHz/24-bit audio.

[edit] HDMI 1.1

Released May 2004.

* Added support for DVD Audio.

[edit] HDMI 1.2

Released August 2005.

* Added support for One Bit Audio, used on Super Audio CDs, up to 8 channels.
* Availability of HDMI Type A connector for PC sources.
* Ability for PC sources to use native RGB color-space while retaining the option to support the YCbCr CE color space.
* Requirement for HDMI 1.2 and later displays to support low-voltage sources.

[edit] HDMI 1.2a

Released December 2005.

* Fully specifies Consumer Electronic Control (CEC) features, command sets, and CEC compliance tests.

[edit] HDMI 1.3

Released 22 June 2006.[7] [8]

* Increases single-link bandwidth to 340 MHz (10.2 Gbps)
* Optionally supports 30-bit, 36-bit, and 48-bit xvYCC with Deep Color or over one billion colors, up from 24-bit sRGB or YCbCr in previous versions.
* Incorporates automatic audio syncing (lip sync) capability.
* Supports output of Dolby TrueHD and DTS-HD Master Audio streams for external decoding by AV receivers.[9] TrueHD and DTS-HD are lossless audio codec formats used on HD DVDs and Blu-ray Discs. If the disc player can decode these streams into uncompressed audio, then HDMI 1.3 is not necessary, as all versions of HDMI can transport uncompressed audio.
* Availability of a new mini connector for devices such as camcorders.[10]
* The Sony PlayStation 3 is the first product available on consumer market with HDMI 1.3.[11]
* Epson has released the EMP-TW1000 as the first display supporting 30-bit deep color.[12]

[edit] HDMI 1.3a

Released 10 November 2006.[13]

* Cable and Sink modifications for Type C
* Source termination recommendation
* Removed undershoot and maximum rise/fall time limits.
* CEC capacitance limits changed
* RGB video quantization range clarification
* CEC commands for timer control brought back in an altered form, audio control commands added.
* Concurrently released compliance test specification included.