What you want is something light, breathable, and water-resistant without being waterproof (I assume you are prudent enough not to run in a downpour).
Pearl Izumis Infinity Jacket ($79) fits that description perfectly. Its made of Pearl Izumis Zephrr fabric that is mostly polyester, a material that is naturally water-resistant and also breathes well. Its just about windproof, is very light, and has stretch fabric through the shoulders for more comfort. I wear the biking equivalent on a regular basis, and its great.
Another excellent piece is the Adidas Supernova ($99), which uses Gore Windstopper. Windstopper is a highly breathable material that has perhaps a touch more water-resistance than the Pearl Izumi jacket. Its a little heavier, too, but still a great piece of running apparel. Its trimly cut and has a pocket for an iPod.
Layer either over a lightweight base, such as Icebreakers Atlas Half Zip ($65), and youve got a great set of cool-weather gear.
I dont like shells over my legs; I always prefer some sort of tight or legging. If its damp out, your legs dont mind as much as your torso, anyway. Nikes Pro Winter Tight ($50) is a top-notch mid-weight tight that will keep you comfortable.
Have a great winter of running!
The 2008-09 Winter Outside Buyers Guide is on newsstands now. Look for it online soon so you can get prepped for gift-giving seasoneven if everything you pick is for yourself!