The other day, I spoke with a retired physician who is now completing an executive MBA program. This person is retiring from medicine (after many years of clinical practice) and is now embarking on several new business ventures.
Many physicians don't realize that business can be very fun. If you have a great business idea, you could take those ideas and create a company and generate a significant amount of revenue (if it's the right type of business model). If it's not a great business model, you may still have some fun if you're doing something fun and interesting.
Are you an entrepreneur? Recently, I've been listening to many different podcasts through iTunes that focus on business and entrepreneurship. Stanford, Wharton, and several other business schools have some great podcasts on iTunes U. It's free education!