Just wondering what holds up well in like 40 degree weather. The last few nights it has been positively FRIGID on the ride home!.

when it gets freezing here in scotland i wear a feather puffer jacket under my riding jacket, you want something that is light but holds air. so a feather jacket is perfect.
also a neck warmer is a must for stopping air coming into your helmet. and decent gloves. i use two layer ski gloves. but heated hand grips wouldnt go astray.

Be sure to layer. hmmmnz is right in saying that trapping air is important. Layer a long sleeve shirt with a short sleeve. Get a hoodie over that too and poke the hood out of your jacket so it doubles as a neck warmer. Also look into getting a balaclava and some glove liners. Balaclavas keep your head and face warm, while glove liners keep your hands warm. Thermal underwear goes a long way in cold weather.

Thermals under your gear works. I've got a polar fleece neckwarmer that works really well & I've got a neoprene face mask that makes you look like Phaedrus (or his avatar anyway), that also works well. The coldest I've ridden in since I've got my gear sorted out is around -2C.

I've ridden a fair bit at or around freezing point. fleece is good, layers are the key, two or three T-shirts are warmer than a chunky woolen sweater.

Glove liners essential in the cold but I found that on rides of over (about) an hour the upper leg suffered most and once the shiver sets in it stays with you for a long time after the ride. The only way i found to overcome that was good-old-fashioned thermal L-Js or I have a pair of double-skin quilt lined rain trousers over normal riding gear, sometimes all the lot!

We are all different (thankfully) and some people suffer from cold feet, once again a couple of pairs of thin socks beats one thick sock.

Make sure you stay dry, get a rain-suit, the combination of wet and cold can be a killer. If you ride a lot in cold wear the rain suit anyway just think of it as another layer.

Jeeeeeez, pra'ps I should move to Spain.

I find hands are the hardest to keep warm.  A few layers and a wind-proof outer layer will keep your body warm.

I find I don't ride below 0 celcius just because my helmet visor fogs up too much.

TourMaster silk glove liners $10
TourMaster ColdFront Carbon gloves ~$80
Fog City ProShield for visor ~$17

I have the Firstgear Magnum jacket.

It's pretty damn warm with the liner in and a long sleeve shirt under it.  It's just big enough that I can squeeze a small hoodie under it (I stole my sister's hoodie, it works perfectly).  I've ridden in 35° weather with that jacket, thermal shirt, and a thin hoodie...  I was a little cold, but nothing worth complaining about.  At least for 45 minutes on the freeway...

When it's raining or cold, I wear my Teknic SPRINT II pants.

They have a liner that is almost too hot...  In 35° weather I usually wore thermals under jeans, then the pants...  Again...  Just a little cold, but not bad at all.

I have the same gloves as scratch:  Tour Master - Cold Front Carbon

They are thick and warm, but in 35° weather my hands were a little too cold after about 30 minutes on the freeway...  I can't really fit liners under 'em (although, I haven't tried the silk ones)...

BUT!!!  I hear that hand-guards make all the difference in the world...  Check out this tread on the subject... "They're not a direct bolt-on - some futzing is required.  A dremel and a bunch of washers."

Yeah last night was a female dog with a capital B.

I used a hoodie under my jacket and that worked very well, my hands were a little cold but not too bad.

Feet held up fine, but it's the upper legs that get me. Hard to have the fine control you need when you're shivering so hard!

http://www.motostrano-store.com/icbapa.html Those look like they would work well, but here's the problem.

In reno the high will top 95 and the low will go under 45 in one day! I really hate chaps (Y M C A!) but I'm actually thinking about it.

Just about any waterproof pants will do ya' just fine...  They'll cut the wind and cut the cold...

Keep 'em in a bag or something.

I put mine in my top case.

What is this "cold" I keep hearing about?

Seriously though, I find my Joe Rocket Alter Ego gear is warm (a bit too warm even) down to about 40 F.  That's the coldest I've tried. 

It's layered, so I also wore it today.  It's a bit hot though.  I really want some of that white Fieldshear mesh....

move to a warmer climate ,seriously

Yeah, like Egaeus said, the Joe Rocket Alter Ego is a good layered/rainproof jacket. My wife has one and it seems to be pretty warm for her on the cooler days. I have a Joe Rocket Meteor 5.0 which is the slightly cheaper version, but has a liner. It's fine in 35-40 degree weather on short trips--like 15 minutes, with only a long sleeved t-shirt underneath.