It is a good project if maybe you aren't the best sewer, like me, but are enthusiastic about crafting.
(And all of this out of one pair of socks!)
Step 1: Finding your socks.
Cut them in three pieces. I had already cut these before I decided to make this instructable, so please imagine they are all in one piece. First you cut the toes off, (I used pinking shears) then you cut the top bands off. The toes we will use for our sock monkey and our MP-3 cover. The main part of the sock for our arm warmers, and the top bands for our ponytail holders.
For the arm warmers, cut about a 1/2 inch hole in the heel of the sock for your thumb. you can add a trim around the top and bottom edges if you like, and then sew it on. Make sure that you have enough trim to fit around your hand (and arm) comfortably. It might work better if you use a stretchy trim. For the record, whenever I tried to zig-zag the edges of the sock, it wanted to stretch and be wavy. You could use this to your advantage if you want to put a "Lettuce edge" on them. You can also just let the edge roll down and whip-stich it into place by hand, which is my personal choice. If you straight stitch it, it works better, but then it doesn't really stretch.