I believe there are also some good tools out there for printing larger quantities of data onto paper, using ECCs and such. QR codes and other such optical encodings are generally designed for much less optimal environments and smaller data sizes; with a laser printer and a good scanner, fairly good data densities can be achieved.

It's an interesting area of research/hacking. Personally I rather love the idea of the Rosetta Project: http://rosettaproject.org/disk/concept/