I have just started some weekend volunteer work for a charity. For those who have busy consulting careers - like me - but who have no such outside interests, I can highly recommend it. There's nothing exceptional about this, I realise, I just thought I recount my experience.
It's remarkable how ridiculous the day to day irritations of professional life are, compared to the challenges some people face. it's much more than CV padding - give it a go if you are tempted.