Here are a pair of socks that I just finished for my three year old. I didn't use any particular pattern, just basic toe-up socks, 36 sts around on 2.5mm circulars, short-row toes and short-row heels. The yarn is some Socks That Rock medium-weight left over from a previous sock project. Too good to waste, and I love the colours ("january one" colourway).
Working with leftover yarn gave me the problem of not knowing exactly how long I can make the socks. But thanks to digital kitchen scale, I just weighed the ball from time to time so I knew when to wrap things up. I'm glad it turned out to be a pair of decent sized socks!