As promised, I've put together a simple little tutorial for the hanging yarn ball mobile you saw in Cinco's Nursery Reveal.
There are several ways to go about this look, including simply hanging actual balls of yarn. The downside to this would be that the balls of yarn would be quite heavy, and it would require the use of more yarn...
...You can also find tutorials on how to make hanging yarn balls that are light and airy, which I think are also pretty, but really capture a different feel than the ones I've made here. The light and airy version requires cotton yarn, which tends to be a bit more expensive than acrylic. I personally would go for light and airy if using decorating for a wedding or perhaps for use in a little girl's room...
...In my case, I wanted a very homespun, "chunky," playfully childish look for the nursery, and thus, went with this: