I've just ordered some monitors that can display 1080p video. When I orient them in a certain way, I'll be able to play back 2160p (Quad HD) video.
I've looked across the Internet (YouTube, download sites), but have been able to find very little 2160p video. Where can I find more?
Short answer, you can't.
Barely anything whatsoever (Other than $10,000+ professional equipment) at the moment can record in higher than 1080p video - well, I have seen a few consumer products that "can" record at higher resolutions, but it is just digital magnification / the actual quality is beyond poor.
As for streaming, I can't even imagine what the required bandwidth would be. (but I guess it is usable - just wouldn't expect many sites to offer it for free).
Anything that can record natively at above 1080p is just far to expensive at the moment... And you will need the graphics horsepower to be able to play it back - there are no consumer players out there able to view it (computers are usually just an after thought) so without the entire eco-system, it just won't be popular for some time.
What I would recommend you do is get a good player that supports multi screens and upscale the content to play across all of them.
I know it isn't really what you want to hear, but I think until Quad HD becomes mainstream, it is going to be pretty much the best you can do.
Some standardized resolutions above 1080P are 2K (2048x1080), 1440P (2560x1440), 4K (4096x2160), 2540P (4520x2540), and UHDTV/8k (7680x2540).
You can download a trailer for the short film Crossing the Line from http://www.red.com/shot_on_red/ (scroll down to the bottom). It was shot at 4k but I'm not sure if full sized clips are available. Some direct links are listed in the first post at http://www.redcamcentral.com/forum/viewtopic.php?t=17&sid=09c87e1c884eb681c6957452c1f85924
YouTube added some "4k" footage a while back... highly compressed. Not sure if it really counts. http://www.youtube.com/view_play_list?p=5BF9E09ECEC8F88F
For now ATI Eyefinity is the closest you can get to experiencing the Quad HD quality.
As for videos: Try to create a panorama video, according to Google it's possible... ;-)
There is an episode of MacBreak shot in 4K on a RED camera. You can watch it on youtube in its original resolution (note the choice "Original" above 1080p in the quality selector).
There are a few examples of 2160p video located at http://media.xiph.org/video/derf/ (search on the page for the term "2160p".
These examples are raw movie files (only 500 frames at 5.8GB each) and are mostly used for performance testing. Typical application could be a 2x2 videowall running 1080p on each monitor, for example.
