FEX is great to cross organizational boundaries (that is, whenever ssh isn't an option). It's actively developed too.
For non technical users we're also having DL, self-hosted as well. It includes a thunderbird extension that cut our usage of attachments to zero.
I understand why this isn't a widespread solution, but it works great, and use it to share big files with non-technical folks (just give them the ngrok link).
F*EX (Frams' Fast File EXchange) is a service to send
big (large, huge, giant, ...) files from a user A
to a user B.
The sender uploads the file to the F*EX server
using a WWW upload form and the recipient
automatically gets a notification e-mail with
Feature request: https