I went to a risk management course recently that was put on by my malpractice insurer.  They entice you to go by offering a 7.5% discount on your premiums for the next 3 years.  I've been to a lot of risk management CME in the last few years.  In fact, it seems like half of the CME I do is more about fending off lawyers than actually taking care of patients.  At any rate, I was consoled by the fact that I was making a lot of money while I was there.  Here's my calculation:

My malpractice insurance is something like $18,000 a year.  7.5% of this is $1350.  Since this discount lasts for 3 years, I'm really saving $1350 x 3 years = $4050 by attending this course.  I spent 7 hours at the seminar, so that's $4050/7= $579 per hour, far more than I make seeing patients in the ED.

In reality, my insurance is probably overpriced by about $1350 per year and this is just their way of making sure you come in and get the training.  But either way, to me it was a very profitable way to spend a Saturday, even if it wasn't as fun as going skiing.  Sometimes saving money is just as lucrative as earning money.  Saving money sometimes also gives you the benefit of giving you tax-free money.  That wasn't the case with this, since I pay for malpractice insurance pre-tax as a business expense, but if it was my auto insurance or something that I would pay for after-tax, then it would be worth 33% more.

What lucrative opportunities have you found to save a lot of money with very little time or effort?