There are just so many options available and it completely depends on how secure you want/need it. As others said, DropBox is a great option, or you could get a hosted server and run FTP pretty cheaply. Hamachi VPN is secure and easy. Depending on the size of what you want to share you could even use a free Google Apps account. Being that the internet is a huge mechanism for sharing data with others this could be an endless list.
As for sneakernet, you could get a set of thumb drives or external drives and use a folder sync tool, then just pass the drive(s) around to the group of sharers.
I use a combination of hosted FTP, Google Apps and Picasa to share files. It all depends on what exactly you want to share and who you want to share it with.