The problem is, they're all creating files for the website and I always have to change the group to www-data so they have permission to it. I can run a cron job, but that seems like a ghetto fix. The users are creating a file locally and just transferring it via SFTP through programs such as Transmit. I am sure I am not the only one having this problem, so I wanted to know how others handled it.
This is the setup I used: http://library.linode.com/security/sftp-jails
Set the group of the directory to the group you want and then set the sgid permission bit. That should do the trick.