Efunda, I have an idea for you guys.
I have to fall in with Rstone and Acroduster on this, I think a user supported "download" section is a nice idea. I have several spreadsheets I've used in the past. some I wrote myself, some I've aquired from others, some are hybrids. Not all of them are polished, some were thrown together to solve a specific problem etc. I don't mind sharing those spreadsheets I wrote with the rest of the world. some of my favorites are spreadsheets for designing compression springs, pressure vessels, and winch drum capacity.
ALL THAT BEING SAID... a big issue would be security. how do you prevent the uploading and downloading of viruses/worms? what about copyright issues? how do you keep someone from uploading a spreadsheet owned by somebody else? could efunda find themselves being sued for making copyrighted material available? what about people who would upload things like kiddie porn and pirated movies. if efunda exercised editorial control to prevent that could they then say that they had no control over what the users uploaded if it was found that someone elses spreadsheet was found on the site? that is a legal two edged sword. these are very real legal issues and not to be taken lightly.