American Express experiments with phased retirement:
Rather than retiring and leaving the company at once, participants gradually give up their day-to-day responsibilities, while replacing some of their free time with activities like mentoring and teaching master classes to their successors. In addition, they get more time out of the office doing whatever they wantbe it planning for life in retirement or doing charity work. The phased retiree continues to receive a portion of his previous salary, benefits as usual, and the company in turn gets to hold on to some of its most valuable employees a year or more past traditional retirement age.
(Hat tip: Good)