Yarn: Any feltable yarn. I've been using my hand-dyed yarn, Paton's Wool, LB Fisherman's wool, Paton's SWS (the color I used bled), LB Landscapes yarn. Whatever I have that will felt.
Needles: Knitpicks Options (of course) I think I've been using 5s and 8s, depending on the yarn.
Pattern: I made up my own. I do need to write it down still!
Time: These don't take very long at all. They are one of my favorite take-along projects. Just like socks for feet, I usually have one on the needles all of the time.
Notes: I have a bunch of these for sale at My Etsy Shop, with my yarn. Everyone who has used them so far has loved them. Or at least that's what they've said! They make the soap lather really well, and last longer. The wool gives you a little exfoliation. As you use the soap, the wool felts and turns into a solid piece of fabric around the soap. I love knitting and using these. They also make wonderful gifts.
More posts on my soap socks can be seen here.
edit 3-25: I have discovered that some of the dyes and the soaps react and run a little bit when you first use the soap. You may have colorful suds, but no one has gotten dyed hands. The colors of the yarn may fade a little bit, too, but it takes quite a while. I've been using my soap since December and it isn't faded, and the suds aren't colorful anymore. :( These are still great projects, maybe I need a lighter scented soap or something.