A great free and secure sFTP server.
FTP by itself is very insecure. Passwords are sent in plaintext over the internet; there is no encryption. You can set up FTP with an SSL certificate, but it can be complicated. This is where sFTP comes in. sFTP is FTP encryped with an SSH layer. freeFTPd is a free sFTP server. It's very easy to set up the server, set up users, view logs etc. Its a lot more secure than FTP.