- ownCloud has desktop client applications that sync files automatically onto the server and back between multiple clients (like dropbox).
- It provides a caldav server for calendar sharing.
- You may share files with single or groups of people.
- Web gallery for uploaded image files.
External user authentication
The ownCloud apps repository contains user_external which allows one to authenticate against a FTP, IMAP or SMB server. Since I run my own mail server, authentication against IMAP is my preferred choice to keep my passwords list short.
Determined to solve the problem once for all, I followed the hints and rewrote a large part of the external authentication plugin.
One and a half months later, both patches got merged in git master. With ownCloud 7 you'll be able to enjoy them, too.