I forgot to mention, as others have, you don't have to get the expensive ones. I use some Performance brand things that were on sale for like $2 each. Not cheap for socks, but pretty cheap for cycling socks. Plus they don't have graphics (except a small 'P'), and they come in colors to match your kits.

Ok, so I went and looked, and they're the Performance Team ones. No cotton, and they're $7 on sale, $8 normally. Kind of expensive I guess for socks, but I like them.