I have wanted to make some of these for quite a long time.
Again, Sandra beat me to it; even with a tutorial on her blog.
Last night, I pulled out the wool yarn and started creating.
Here are some before I felted them.
And here's the ones I have already felted.
I had a bunch of leftover wool yarn on hand, so I just made wool balls until I thought I was done, then I found enough more wool yarn to make probably 15-20 more!
Now, I tried something a little different than Sandra didn't do in her tutorial. For the center "core" I wound the yarn very tightly for the first 1/4 of the ball on some, others I didn't. I found that the ones with the tighter wound core were a bit heavier (and bouncier), so I think they may do better in the dryer. Also, I used panty hose, and instead of tying with string, I just knotted the hose very close to each ball as I put it inside the hose. After they were felted, I just cut the hose to get them out. You will likely find some of the wool balls stuck to the hose when you attempt to remove them. That is fine, just pry the hose off and it's ready to go.