apt-get install vsftpd
Then change the following in the file /etc/vsftpd.conf
anonymous_enable=NO local_enable=YES write_enable=YES chroot_local_user=YES
Now you need to reboot the service
This works very well with user accounts on the machine.
UPDATE: I had some problems with people posting files and the permission where always read only for websites. Just add this to the CONF file and things should work better