This is a terrific topic and should also include all the social innovation around older adults as contributors/resources (as opposed to recipients/liabilities).
In particular, there's an emerging trend toward hybrid "encore careers" that combine giving back (giving forward?) and continued income. Check out www.encore.org and www.civicventures.org for a trove of leads/links/stories, or drop me a line at dbank@civicventures.org.
cheers,
David