LionShare might be the answer for informal sharing in the way described as a model in an earlier entry. It originated at Pennsylvania State University and looks similar to the Limewire P2P software using the Gnutella network client.
Authorisation can be linked into the institutions directory service, thus it shall be secure and governed by local policies of acceptable use. LionShare also features collection management and automatic metatagging to ease sharing of image files and academic content. It does not allow anonymous uploads so perpetrators of copyright can be identified and disciplined.