nix based ftp server suggestions

Hi all,
I was wondering if anyone had any suggestions for a secure ftp server with
easy to manage user setup.
Needs to be
1. nix based
2. easy user setup(user having ability to change their own passwords would
be cool)
3. Easy to manage
4. Something people could use their browser to download/upload from.

I've seen Rumpus in action but it is mac based.
Open source would be best!