I spent a bunch of time, money, and effort to research cold weather riding and running gear and figured I’d share what I’ve found with the fine folks here at ST.
I had previously posted some info/links, but have since discovered a few new items that are less expensive and more effective, even in the wind and rain. It’s been abnormally cold here in WI lately, so this system has been tested quite a bit over the past few weeks.
If you have any experiences, tips or tricks, I’d love to hear about them, because this is by no means “definitive.” 
Top Half:
Nipples: Body Glide Anti-Chafe ($10 MSRP)
Cold, sweaty nipples + fabric = ouch. This stuff will protect your sensitive bits, and it doesn’t add any odor/scent, isn’t sticky, and I’ve used it on 5-6 hour brick workouts without wearing off. Great, great, great stuff.
Link: http://www.bodyglide.com/#/products/anti-chafe
Base Layer: Icebreaker Atlas 150 ($60 MSRP; can find on sale online)
100% high quality Merino wool. It wicks sweat like nothing else, regulates your body temperature, breathes well, and feels like you’re wearing nothing at all. Forget all you thought you knew about “wool” - this stuff is incredible. Itch-free, non-fuzzy; it’s super lightweight, yet works as an excellent base layer. You can wear it multiple, multiple times without washing it - it won’t hold odor, won’t lose its shape, and won’t wear out anytime soon. It’s worth any cost, even at $60, but you can find it online for less if you do some digging.
Link: http://www.icebreaker.com/site/icebreaker_man_bodyfit150_ls_atlas.html
Insulation Layer: Icebreaker Slalom Crewe 260 ($99 MSRP)
For temperatures that range from 35 - 60F, you can easily get away with wearing just this layer and the base layer. This Insulating Layer has all of the same benefits of the base layer - I can’t say enough good things about the IceBreaker line of clothing. If I ever come into a windfall of money, I’m going to stock my entire closet with IceBreaker stuff. It’s cut “athletic” - pay attention to their sizing guides.
Link: http://www.icebreaker.com/site/icebreaker_man_bodyfit260_slalom_crewe.html
Insulation Layer #2: One More Mile Wick-Lite Fleece ($15 on sale)
When the temperatures dip below 35, or it’s windier than normal, I’ll add this layer to the system. Once again, it’s a super light weight piece of clothing - so light in fact that I had my doubts about its effectiveness. But, I’ve worn it while running in single digit temperatures and have still managed to work up a ridiculous sweat. It breathes well, but will hold odor, unlike the IceBreaker stuff, so you’ll have to wash it a bit more often.
Waterproof Layer: Pearl Izumi Fly Jacket ($90 MSRP)
A great, inexpensive “shell” layer that’ll protect you against the severe elements - wind and rain. Very lightweight, very versatile. I wear this jacket when the weather is really nasty - we had a torrential downpour today; I logged 11 miles by foot and didn’t feel a drop of rain. I also have the $100 Pearl Izumi Elite Barrier Jacket - it works well, too, but the Fly is $10 less and I wear it more often.
Link: http://www.pearlizumi.com/product.php?mode=view&pc_id=33&product_id=1319620&outlet=
Gloves: Cheap Thinsulate gloves ($10) from local ski store + Pearl Izumi Soft Shell glove ($45) for water/windproofing
Hop into any local ski/winter store and buy a pair of the thin fleece-like Thinsulate gloves. Use them alone on non-windy/non-wet days, or use them under the Pearl Izumi gloves for a bit of extra insulation on those really cold days. The Pearl Gloves are awesome - great feedback/feel, comfy, windproof, waterproof, and versatile. Well worth the $45.
Link: http://www.pearlizumi.com/product.php?mode=view&pc_id=73&product_id=1455046&outlet=
Head: One More Mile Beanie ($12 MSRP)
Fleece lined for wind-resistance. Fits under my bicycle helmet without any problems, and is totally warm - in fact, it’s so warm that I only wear it when the temps dip below 30F, otherwise I feel too warm. A pair of those “ear muffs” work great for warmer days - you can find them at just about any ski store or even from places like Walgreens and Tractor Supply.
Link: http://www.onemoremilerunning.com/headwear/beanies/will-run-for-beer-beanie/prod_245.html
Results
With all of the layers donned, I’ve rode 60+ miles and run 10+ miles in weather that was 21F with a 20mph wind (gusts to 33mph) and been completely comfortable.
For most days, when the weather is 30-35, I skip the waterproof layer and wear only the fleece gloves; when the mercury hits 40F, I skip the Insulation Layer #2 and just wear the IceBreaker layers. Generally speaking, I’m very “cold blooded” and tend to “freeze” easily… this stuff has literally enabled me to ride/run/train in almost any weather condition with complete comfort.
Bottom Half:
Riding shorts: Normal riding bibs (I have several pair of Sugoi)
Riding/running pants: Sport Hill XC pants ($105 MSRP)
I picked-up a pair of these at a local outdoors store that was moving locations and “stole” them for $44. What an investment. They’re 100% windproof and 100% water resistant, and they have a tremendous amount of insulation - so much in fact, that I can really only wear them when it’s really cold out. Otherwise my legs get too warm. I’m going to buy another pair for spare duty and will happily pay $100 for them - they’re really worth it. I wear them over my riding bibs (or under my running shorts). They’d also make a great “long underwear” for those cold, snow-shoveling days and will fit under your blue jeans without any problems - they’re thin and light.
Link: http://www.sporthill.com/product.php?TypeID=2100&gender=m
Pants - alternative/cool weather: UnderArmor Cold Gear ($55 MSRP)
You can find these at almost any sporting goods store, and I tend to wear them more often than the Sport Hill pants because they aren’t quite as warm. They offer decent wind resistance, which is nice; I can wear them under my bibs and ride in temps that dip below 45 while still being completely comfortable.
Socks: Smartwool (any type will do - they rock)
My only tip: buy these from Sierra Trading Post’s website. They’re about half the price while not sacrificing any quality from full retail versions. STP sells 2nds and blemished models, but they’re still fine.
Summary
So… for around $300 you can get a “go anywhere, do anything, anytime” solution for your upper half, and for around $175 (with socks), you can take care of the legs. It sounds expensive, but this stuff will last you a long time and is versatile enough to use in a wide variety of conditions. No “uni-taskers” here.
Hope this info is beneficial to some folks.