Need suggestions on a shared storage system for a charity

I'm volunteering with a charity in India that has a need for a shared storage system. They have multiple facilities scattered throughout Mumbai, and each facility has at least one computer with an Internet connection. There's no intranet or central server that is accessible from every facility.

I was thinking about setting up a hierarchy of Google Docs accounts for them to use for data storage since it's a rough physical environment where hardware failures are common, but is there a better solution out there? Every computer has MS Office on it, so there's no need for online editing capability. Free services are preferred, but low-cost may be an option as well. Multiple accounts are necessary since not every user should have access to every document.

Thanks for your suggestions. The charity does a lot of work with HIV+ orphans and families affected by HIV, so it's definitely for a good cause.

I still think dropbox is the killer app out there, but there are some alternatives; SugarSync (never tried it but I've heard it's pretty good). is one of the new players and they're offering aggressive locker sizes (5GB+) in order to quickly gain market share.

I know for sure that dropbox is perpetually free, I'm not sure about the other too, but my guess is they follow the freemium model.