A few quick disclaimers: I am dividing this into "transport" and "sport" sections, because for me the two rarely intersect, not because I think others must keep them separate. Also, you will find that some things here are female-biased, because, well I am female. Finally, I linked to some companies and products, because readers tend to ask for specifics. As always, none of the product mentions are endorsements or "monetised" in any way; they are just there for your info.
Pictured here is the sort of thing I normally wear when getting around by bike, either for work or errands. I will start from the inside out.
Worn closest to the body, underwear plays a crucial role in temperature regulation. So before I worry about bundling up, I make sure to get this part right. In my experience, underwear made of wool, silk, lycra/spandex and some technical polyester-based fabrics, is generally good at regulating body temperature and wicking moisture. Underwear made of cotton or acrylic is not. Out of the fabrics that work I prefer wool and most of my undergarments are from Ibex: I like their modern and stretchy wool/lycra blend. Icebreaker and Smartwool also offer some good options, as does Winter Silks if you're looking for budget-friendly silk.
My everyday clothing ranges from casual to formal, but, especially in winter, it almost always involves skirts and dresses. This is because I find it easier to add warm layers under a skirt (wool leggings or legwarmers over tights), than to deal with layering under trousers or jeans. Also, if it rains or snows, tights with knee-high boots are a highly effective way to keep dry. After several winters of experimenting, most of my cold-weather outfits are now wool. I knit wool skirts myself in variety of styles. And I wear wool sweaters over wool or silk base layers. 100% merino is harder to find now in mainstream stores than it used to be, but J. Crew remains a good source and they have frequent sales (like right now). I also alternate between several wool dresses, mostly handmade. And I still own a few wool skirt-suits from my suit wearing days. If I want to wear an outfit that is made of a non-temperature regulating fabric, I will wear a wool or silk baselayer under it and it'll be fine. But to me, wooly stuff just feels overall warmer and cozier.
When buying cold-weather tights, I look for wool and nylon/ lycra/ spandex content, and I avoid cotton and acrylic content - because, as with baselayers and underwear, the latter does not wick moisture or regulate temperature well. Smartwool makes decent all-around winter tights (and socks). Falke is a European favourite, but expensive. Another option is to wear dense nylon tights (such as these), with wool leggings or legwarmers over them, which can be later removed indoors.
Both on the bike and off, I am a fan of waterproof boots rated for freezing temperatures. For years, I have been wearing La Canadienne boots that are exactly that. I have a pair of their ankle boots and a pair of knee-high boots that look reasonably professional and feminine, while being absolutely winter-proof. The soles have excellent traction on snow and ice, which is also useful for when my bike pedals turn slippery. With the knee-high boots, the additional benefit is that they keep my legs extra warm, and protected from slushy splash-back.
On the bike, I favour wool 3/4 length coats with an A-line shape, so that the hem does not constrict pedaling. The coat should fit loosely enough to allow layering underneath, and should not in itself be too warm. When I am walking, I will sometimes wear a down-filled coat, but I find it too bulky when cycling. The down-filled coats can also be slippery on the bike saddle, whereas wool coats stay put. My current coat is about 6 years old and I no longer remember where I bought it.
Usually I wear a wool beret or hat that I knit myself. I take care that the stitching is dense enough to be wind-proof, and that the hat covers my ears.
My favourite gloves for cycling are wool and grippy. They are perhaps not the most elegant choice, but their functionality has won me over.
After some experimenting, I have taken to wearing a shawl-like wool scarf which I wrap around my neck once and then tuck the rest into the front of my coat for an extra layer of warmth over the chest. This really helps when cycling against an icy headwind. Beware of long, flowing scarves on the bike, for obvious reasons.
Want more winter wardrobe advice from genuine cycling fashionistas? Dottie of Let's Go Ride a Bike has excellent tips from snowy Chicago. Here is her latest post on the topic and a more general guide for winter dressing. Also, this excellent Bikeyface post will not disappoint.
With roadcycling, I find getting dressed in the winter easier, simply because there is less creativity required. I can wear the same thing over and over! Here is my formula:
I like thin, long sleeve wool base layers. There are many options to choose from now. Rivendell has come out with a nice US-made one recently. I also wear a wool/lycra sportsbra underneath (see "Underwear" earlier).
In winter temperatures, I wear fleece-lined full length tights. I have tried bib tights, but ultimately I find them too fussy to get in and out of. I prefer the padded winter waist-high tights from Capo, and wear a model from a few seasons ago. In addition to being super warm, these are also somewhat water resistant. I have made do without rain or snow pants so far, and have not felt the need for them.
I love the simplicity and longevity of DeFeet wool socks. Of all the wool and wool-blend socks I've tried; they have been the most durable. When it gets particularly cold, I wear two pairs.
My midlayer is a winter-weight long sleeve cycling jersey. As long as I wear a wool baselayer, it does not matter to me what the midlayer jersey is made of, as long as it insulates. I own a few now, but my favourites have become the wool/poly blends from Rapha and Shutt Velo Rapide. These are wool on the inside, with some high-tech poly coating on the outside. I do not like how they feel against the skin, but as midlayers I find that they offer the best temperature regulation.
Winter outer layers are tricky. A windbreaker/shell type jacket is not enough. A jacket that's too warm can be even worse. Last winter I bought a Rapha winter jacket on the recommendation of some of the women I rode with, and it is just right, even for the coldest temps around these parts. This is a painfully expensive jacket, but it does go on sale occasionally and stalking it was worth it.
DeFeet Duraglove. I have tried fancier and supposedly more weather-proof gloves, but prefer the DeFeets. Gosh, I hope they never discontinue these.
These are called various things, depending on the manufacturer, including neck gaiter and collar. I have a few and find them very useful. For extremely cold rides, I have tried a balaclava, but it is not my cup of tea; I prefer to wear a neck warmer and pull it over my mouth instead.
I wear a tightly knit wool winter cycling caps with brims and ear flaps. I buy these instead of knitting them myself, because I can't get the weave tight enough by hand; it has to be machine-made. Several companies offer these hats now. I have one from Bicycle Fixation and another from Ibex. I usually wear a helmet on my roadbike, and find that this adds to the cap's warmth, while also helping to keep it firmly in place.
I do not own winter cycling shoes at the moment, though I hear there are some wonder-boots from Lake that are pretty good and I might save up for those eventually. I have some overshoes on loan from the Ride Studio Cafe, but I have to admit they scare me, so I have yet to try them. Instead I just wear multiple pairs of socks for now. My toes have only frozen a couple of times so far...
Want winter wardrobe advice from more experienced roadies? The Blayleys have an excellent series of posts on this topic here, here and here. As they probably spend more time on the bike in the winter than off, they are the best source I know.
Keep warm and enjoy yourself on the bike this winter, whether in sport or transport!