The most common and least expensive are covers. These are kind of like blankets that attach to the carrier and keep baby covered. The Monkey Pocket and Winter Carrier Cover by CatBird are both examples of covers.
Then there is the Peekaru Original which is a fleece vest that zips over both you and baby completely covering you on all sides. These are nice because they can be worn under a coat, but give you coverage completely up to your neck, unlike the covers which only cover the baby. Suse Kinder also makes a fleece babywearing vest.
Hoppediz makes a fleece cover that is kind of a cross between a cover and a vest. Find out more by reading this detailed article.
Finally are the more expensive coats and ponchos like Suse's Kindercoat and Peekaru Soft Shell that are designed specifically for babywearing. These are the most expensive option, but are a great option if you are not on a budget.
Fall/Winter Babywearing on a Budget
You don't have to be rich to babywear this winter. The best option is to use any over sized coat or jacket. You can go buy one specifically for babywearing (you can find lots of good deals at stores and resale shops), use your husband's or mother's like I did, or use your old maternity coat if you were lucky enough to have bought one.
An over sized jacket or coat can be easily zipped up over both you and your baby. This only works well for front carries, but I preferred front carries in winter anyway so I could keep a close eye on how my baby was handling the cold.
You can tuck a blanket around baby for extra warmth when it is really cold, similar to how covers work. Like with covers, your chest and neck will be exposed when using a jacket/coat since you can't zip all the way up, so you will want to make sure you are wearing something warm underneath or use a scarf to protect your chest and neck area. Luckily, babywearing in winter does have the benefit of keeping both of you warmer!
If you are crafty, you can always make your own babywearing coat or poncho. There are lots of patterns you can find on-line. This isn't always a cheap option since it depends on what you decide to make and the materials required, but it can definitely save you some money, especially when it comes to babywearing coats.
Happy Babywearing and enjoy the weather!
Update to respond to Chrissy's question:
One issue I'm trying to figure out is something quick and easy so I can get the baby in quickly if I don't have her bundled and we're getting her from her carseat to the carrier in a parking lot in a blizzard. I'm thinking a stretchy wrap might be good for this so I could have it pre-tied and ready to go, then baby is under 3 layers of fabric while I get the cover on. What do you like to use?
First, I never have my baby's bundled when they are in their carseat. It is actually not safe to have a heavy coat on underneath the straps of a carseat because it can be unsafe in an accident. To find out more, read this article.
Because my daughter only wore a thinner jacket (usually a fleece hoodie) in the car, I was always faced with this situation when babywearing in winter. What I did really depended on where I was going. I usually did put the carrier on at home first with my coat over the top, especially with sometime like a stretch wrap or ring sling, but that was mostly so I didn't have to do it when I got where I was going.
If I was just going from the car to the store, I would usually just hold my baby while I covered them with a warm blanket and wait until I was in the store to put them in the carrier. This just seemed like the quickest and easiest option. Some people I know would sit in the back seat and put their baby in the carrier before getting out of the car at all. Whether this is something you can do depends greatly on what kind of vehicle you drive and how much room you have.
If I was planning to be outside for any period of time, I honestly just took off my coat in the freezing cold, put the carrier on and in position, then put my daughter in it as quickly as I could before putting my coat back on over both of us! In this situation, it would definitely be easier and quicker to put on a Hopp cover than a babywearing vest, but in most cases, I wouldn't bother unless I was planning to stay outside longer than it would take me to run into a store. I know that sounds a bit crazy, and I'm sure I got lots of looks while standing outside my car strapping some contraption on me and my baby without any coat on, but it worked for us! If you can fit in the back seat of your vehicle, I would probably recommend doing that.
Hope that helps! Have a great winter!