I thought of an idea that would help refill the public domain, which is impoverished today because modern copyright rarely lets anything into common use. Someone -- any sufficiently wealthy person, or a conglomeration of folks -- could buy intellectual properties and then declare them in the public domain.
Rights to characters, novels, comic books, films, etc. change hands all the time. Some are only partial rights, but other times all rights are for sale and that's what would be useful here. Similarly some are expensive, but many are rather cheap and would be readily accessible. People who decide to sell off their intellectual property may be seeking to have it developed, but frequently they just want to get one last bit of money out of something they don't consider very useful.
Look at minor comic book characters, for example, or campy movies; there is often much potential for further development that is unrealized in the original canon but easily accessed through fanworks. Now imagine how much more awesome this would be if those works could be subsequent canon rather than fanworks.
Continuing the idea, crowdfunders might also commission things for the public domain. Some crowdfunding projects are open-source like
Schrodinger's Heroes, licensed through Creative Commons like
nineforthenebulasheart, or otherwise available for people to share. When things are shared instead of hoarded, this tends to make more goodies for everyone to enjoy.