REI Mistral pants. Last fall I bought one pair on sale for half price. One $50 pair of pants that I wore for commuting EVERY DAMN DAY all last winter. My crankset didn't survive but these still soldier on.

Buy some of the Patagonia Capilene. It's very thin, and if you buy it so it's tight on your legs, you don't even feel its presence.

If you're feeling spendy, you could buy some of the new Patagonia wool longjohns, or some Smartwool. Pricey, but I am told by a local cyclist that it's "the bees knees" in the winter.

I've got a couple of pairs of Ex Officio Amphi-pants, which I love.

They've got a built-in mesh brief like a swimsuit, which might cause some chafing, but I have worn tights, padded underwear or whatever was warranted, which worked fine for me. I do like that I don't need to worry about forgetting my underwear. Nothing quite like sitting commando in a meeting.

One thing, which has proven really useful, is a little bungie on the cuffs, which can be buttoned up to make them a little tighter. It keeps the cuff out of my ring.

They're really lightweight fabric, but they have a cotton-like feel --no zip-zip-zip as you walk. They also make convertible models, which are nice for summer.

They're expensive, but can be found marked down on the web. I've been wearing each of them to the office once a week for about 6-7 years, so far, and they still look new, so I think they've actually saved me money over the long-haul.

Oh, and they seem to resist stains pretty well, so if you get spray on your legs, you can wipe it off and let them dry while you wear them.