How can we share large files with people outside of our firewall?

We use a secure ftp server that requires ssl auth. Each project has its own folder under /home/projectdocs/projectname. Each company involved has a login and a sub directory. We usually work with their IT group to script a sync to the source companies external file server. This way the contractors upload the data to a mapped drive within their company's firewall. The data is then syncd to our server every 10 minutes or so. Alternatively we provide the contractor a copy of filezilla to connect to our ftp directly. Filezilla is a great GUI for ftp. No IT knowledge needed.