Just because some thing is free, that doesn't mean that it is not worth having. I have picked up many a free product that has helped me a great deal in learning a lot more about a subject
Many times the free product is a cut down version of the full product which while functional will not give you the complete range of that product. Entrepreneurs do this to introduce you to a product that you may need in your arsenal.
This is a very good way of introducing a new product to a lot of people. They are more likely to download a free version of something and then buy the full version than they are to just buy the full version straight away.
You may find some free products that give you the right to pass them on. They may even have full PLR rights with them.