Got an older
Xbox 360 without HDMI? Well, it seems like there are now two solutions on the market that will solve this problem, the first one which was announced some time comes from XCM and it consists of a somewhat ugly looking disc shaped dongle which attaches to the Xbox 360's A/V connector. It provides HDMI output up to 1080i resolution with separate optical out and RCA connectors for audio in case you want to connect your Xbox 360 do a DVI equiped TV or monitor.
The XCM White 360, as it's called, comes with an HDMI cable as well as an HDMI to DVI adapter. It's available now for €59.95 in Europe and $75.99 in the US. You can find the product page here
Madcatz has a slightly different looking adapter which is much more compact and it attaches directly to the back of the console. It offers HDMI out and a separate optical S/PDIF. It comes with an HDMI cable and an optical audio cable in the box, but no HDMI to DVI adapter. It also lacks the option to output an analog audio signal, but in its defense, it can output a 1080p signal, something that the XCM White 360 can't.
The Madcatz HDMI conversion kit will be available from early next year and Gamestop is listing it for US$89.99 with availability from the first day of next year. You can find a PDF with the product specifications here