Ifolder is one of the free program for file sharing and it is cross platform.
source : www.ifolder.com
Always Know Where Your Files Are
iFolder is a simple and secure storage solution that can increase your productivity by enabling you to back up, access and manage your personal files-from anywhere, at any time. Once you have installed iFolder, you simply save your files locally-as you have always done-and iFolder automatically updates the files on a network server and delivers them to the other machines you use.
Using iFolder, you can designate any network server as an iFolder server and publish information to a personal iFolder created on that server. Once your folder is established, you can install iFolder on the computers you regularly use and download information from your personal iFolder to any of those computers. Not only that, but using iFolder, you can also invite other iFolder users to share your files in the same safe and secure way so that your teams always have the most relevant copy of a document.
What’s new in 3.8
* Multi-level administration
* Active Directory integration for iFolder
* Support for 2.4 runtime environment of server
* Pass phrase recovery wizard
* Changing iFolder account password from webaccess and console and thick clients
* Enhanced User interface for Linux and Windows clients
* Enhanced client startup performance
* iFolder client for openSUSE 11.1, openSUSE 11.2, OS X 10.6 and Windows 7
* 64 bit version of iFolder client on Windows