I'm about to embark on a writing a project to allow my users to subscribe and unsubscribe from a subset of distribution lists. Before I start I did a little research and found an old Microsoft product for exchange 2000 called AutoDL (More).
It allowed people to join and leave groups based upon permissions and it let group administrators add and remove people from their group as well. All from a little web app.
Before I reinvent the wheel, does something like this exist for exchange 2007-2010?