I have only knitted one pair of socks before and they were not a great success (as described here), but only because they were knitted in bamboo yarn and so went very baggy as soon as I wore them. The actual knitting was satisfying - the construction is so clever. This time I wanted to knit them toe-up, because I find casting on for the ankle very fiddly and prone to disasters (like getting a twist into the knitting when you join it up, or dropping a stitch on the first round).
The basic pattern is by Wendy Johnson, free through Ravelry or from her web site (follow the links to "Free Patterns" and then it's the Detailed Toe-up Sock Pattern). Her pattern produces a plain pair of socks - the idea is just to demonstrate the techniques of toe-up socks with a short-row toe and heel. So I used a stitch pattern from Barbara Walker's Treasury to add some texture and interest on the instep and ankle. It's the Vandyke Check pattern (mostly chosen because it has an 8-stitch pattern repeat and I had 64 stitches in total, but it has turned out very well). It is made up of blocks of stocking stitch and reverse stocking stitch, so it doesn't add any bulk. The yarn is 4-ply 75% wool and 25% polyamide from Cygnet, in olive green.