How to make models do more than setting and getting data and validation

Question

I am asking this question because after developing a few small custom cms solutions in a framework, I developed the idea that Models can be easily substituted with ORMs which ease up the task of validating, getting and setting data, as thats all they are needed for.
I recently got an order for a complex custom client management solution. After researching a bit on how to proceed on it, I found this:
http://blog.astrumfutura.com/2008/12/the-m-in-mvc-why-models-are-misunderstood-and-unappreciated/

Now the idea is not new as thats what i had read about the MVC approach, models handle the business logic. But I am finding it hard to plan out an approach in which Models handle the business logic and are classes which are complete in themselves because of the type of work i have gotten used to.
Please help me out here by explaining the idea and pointing me to some examples, articles etc