We can't expect all of the vendors to run out tomorrow and start stamping "Works in linux!" on the box, but someone could at least provide a centralized resource to find out what does and doean't work out of the box in linux.
As for a listing, RedHat already does that: http://hardware.redhat.com/hcl/
I think that attempting to support all current mac perhiperals would be a good start. the number is smaller, the products are mostly USB and firewire, and they already work in a unix based OS. It would be very powerful to say "anything that works in Mac OS X works with Linux". Apple also has already been "nice" to the OSS niche, releasing sources and all.
-- ---------- Doug Stewart Systems Administrator/Web Applications Developer Lockheed Martin Advanced Technology Labs