“Dropbox”-like PlugIn

HI, my apologies if this isn’t the correct forum. Anyhow, I had a previous site that had a file sharing portal (log in, encrypted) capabilities. I used a 3rd party plugin or widget (sorry, don’t know the correct term). My consultants and clients could use it for collaborative purposes, internal employees could get administrative documents, etc.

Any recommendations? I searched most plug-ins but nothing is an obvious choice.

Andrew