Take a look at the "Please Click Here" link on this website and if you want to implement something similar perhaps that site's portal manager can tell you how it was accomplished.
Also a file sync system such as Dropbox shared folders will let you share or collaborate on a set of files.
Dropbox lets you share your folders with others by creating a new shared folder or sharing an existing one. Once you add other members to the folder, it will appear in your friends or colleagues own Dropbox just as it does in yours. Any changes made to the
shared folder's contents will appear almost instantaneously to everyone who is a member of the folder.
All members of a shared folder have full read and write privileges. Setting read-only permissions isn't currently possible, but the feature is on Dropbox's roadmap.
What happens if two people change the same file? If two people or computers change the same file, the person who is the last to save their changed version will "win."