Does Apple sell an adapter for the 30" Cinema HD display that converts the Dual-Link DVI connection to either Display Port (full-size) or HDMI, that isn't going to limit resolution to 1280x800?

Convert the displays dual-link DVI to Mini DisplayPort

http://www.apple.com/shop/product/MB571LL/A/mini-displayport-to-dual-link-dvi-ad apter

then to DisplayPort

https://www.startech.com/Cables/Audio-Video/DisplayPort/6in-DisplayPort-to-Mini- DisplayPort-Video-Cable-Adapter-Male-to-Female~DP2MDPMF6IN

Yes, it's called an "Apple Mini DisplayPort to Dual-Link DVI Adapter."

http://www.apple.com/shop/product/MB571LL/A/mini-displayport-to-dual-link-dvi-ad apter

It is used to connect a 30" Apple Cinema Display to newer Macs.

The 30" Apple Cinema Display has 4 cables that come out of the back:

(1) Dual-Link DVI

(2) USB 2

(3) Firewire 400

(4) Power

Only #1 and #4 referenced above are necessary for the display to function properly. However, for the USB and Firewire ports on the back of the display to function, #2 and #3 referenced above must be connected to your Mac in order to supply them power.

The "Apple Mini DisplayPort to Dual-Link DVI Adapter" does have a USB port that allows the adapter to supply power to the display's two USB ports. However, the adapter does not have a port for Firewire 400, so unless you can plug the Firewire 400 cable directly into your Mac, or you buy another adaptor for the Firewire to be able to plug into your Mac, the Firewire cord out of your 30" ACD goes unused, thus rendering the Firewire ports on the back of the 30" ACD useless.