We have tons of pine cones but no chipper/shredder. Is there a homemade way to grind up the cones into mulch?

I would rent a shredder if possible. You could also dump the cones in your driveway & drive car/truck back & forth over the cones. A bagging mower would also grind them (probably hard on mower). If all this doesn't work, throw them in your compost pile.

Some tough large lawn mowers can do the job very well.
If you use the mower method, throw the chopped up mulch from the machine, toward a tall safe wall.

Happy Gardening!

On my walk this evening in our neighborhood, one of the houses had collected all of their pinecones from their 2 LARGE pine trees and mixed it in with their mulch at the base of all of their trees.

I'm sure it takes a while to break down, but it provided a lot of interest to the landscaping and really looked good as well.

I liked the look of the pine cones piled in the flower beds, but the cones are no so good for stepping into the beds. We finally decided to buy a chipper/shredder, and I love pine cone mulch. It is rich and dark and smells great. I found it helpful to wet the cones so they would close up and fit in the chute better. You have to feed them slowly because they like to wobble around and jam together.
Thanks for all of the great ideas.

Pine cones make great bird seed feeders,spread peanut butter on the cone and then drop them in a bucket with birdseed and then hang outside.
This is a great rainyday treat for the little ones.