BDUs & fatigue pants are great. I used to just wear jeans until I noticed that saddle rub was starting to wear out the seat & the insides of the thighs; BDUs, Carhardts, and good quality cycling pants have reinforced circular seats that don't wear out so quickly. The other nice thing about BDUs is that they tie in at the ankles, which means they don't get caught in your chain.

Also, wool is FABULOUS. Wool sweaters, wool caps, wool scarves, wool socks. I used to live in Utah and on really cold days I wore a pair of surplus Swedish army woolen fatigue pants; all of the above + extra pockets & ankle gussets: toasty warm.