There are only a few options out there for transfering files securely. That's why we developed Rhinofile.
*Self promotion warning*
is a PHP/MySQL application that pushes files onto an internet host, normally a CPANEL hosing provider or a host of your choosing. This could you your DMZ if you are very concious of your data. The application is built so that you choose where you data sits, integrates into your Windows AD authentication. The main difference compared to other applications, is the LAN vmware appliance pushes files onto an internet server. You can expire files after set periods of time, set credentials on the downloads and add policies.
Rhinofile is free, the client is open source so you can review the code going onto the internet host. You just need Vmwware or Xen to boot the image. The image is ioncube encoded(centos).
In regards to the above comments, the best thing an admin can do is provide a service to their staff and the end clients so that they don't have to use these free services. Staff go to the free services because their companies aren't giving them options. Rhinofile has a dropbox where customers can send you staff files as well with some varied options. It's all PHP/MySQL, cron, rsync over SSH etc. Nothing new or fancy.
Any comments on the software would be apreciated as we're trying to find bugs and get more people using it. Bug and security reports will taken seriously but please document it enough so we can pick it up and run with it. The forum is http://forum.rhinofile.com./