Steven J. Vaughan-Nichols has an interesting article on eWeek.com. The title is Making Money From Free Software
He has some interesting quotes from Marten Mickos, the CEO of MySQL AB and how they make money. I think the last paragraph sums it up nicely though:
To be blunt, if you want to profit from open source, you need to be more business-savvy than you would in other businesses. But if you one of these models and make it fly, you can certainly make your living, your first million, heck, maybe even your first billion, from free software.