I also took a few cuttings of a viburnum back in April. These haven't advanced as much as I had hoped but they are alive and well. I haven't fertilized or done anything other than pot them up and water them, even though a little fertilizer will do them some good. It takes time for plants to develop roots and when the roots have reached a large enough size more leaves grow to support the young plant.
If you're interested in learning more about taking cuttings to increase the plants in your landscape take a look at this post: The Basics of Cuttings
Here is a list of 10 easy plants to propagate.
I'll be writing an update post pretty soon about easy plants to propagate so stay tuned!