Miscellaneous tutorials and other junk: How to Stay Warm at Home Without a Heater

So maybe you're a poor college student, or your parents are cheap. Maybe your landlord didn't fix the furnace yet. Maybe you live in an old drafty house. Perhaps you want to curb CO2 emissions. For some reason it's cold and you need new ways of keeping warm. Here they are!

Steps

Close all of your windows properly. This includes making sure storm windows are down if you have them. Windows should be latched.
Keep your windows air-tight. You may want to purchase removable window-caulk or plastic to better seal them. At a minimum, stuff a towel or shirt in front of any noticeable leaks.
Seal your doors. Check around the door frame and also under the door. You may want to buy weather stripping or a door sweep. Again, at minimum, make a draft dodger or stuff a towel at the bottom of the door.
Close off any un-used rooms. The closed door makes that room another barrier between you and the frigid outdoors. It also stops air from circulating as much, which reduces heat loss. Also, home improvement stores sell magnetic register covers to 'shut off' registers in unused rooms. That way when the heater does click on, only the registers in the rooms you use will pump out heat. Makes for more efficient use of the heater.
Put up curtains. A set of heavy curtains can block a draft. Open them when the sun is shining and close them when it's not.
Put down a rug or carpet.
Add insulation in the attic and the crawl space.
Exercise; get in shape. 20 minutes of vigorous exercise can warm you up and keep you warm well after the exercise session. And your healthy body is generally more tolerant of the cold.
Dress warmly. You should wear slippers or socks. Dress in layers, especially with wool or cotton clothing. Wear a hat. Don't wear your winter coat or you will have nothing else to put on when you go outside. When you are sitting still put on a blanket.
Cook. Make cookies or a pie, or a nice, hearty stew! The kitchen will be warm while you are cooking, and then you can eat the warm food.
Drink warm beverages. Make a cup of tea or coffee. Sip some warm broth.
Light a candle. A candle/candles can produce a lot of heat, just be mindful of where they are placed and do not leave them unattended. A trip to most any grocery store or discount store can provide you with a number of candles cheap!
Find a pet or friend to snuggle with. The living body of any warm-blooded being is a furnace unto itself.
Be active. Moving around produces body heat!

Tips

If you can not afford to heat your home, contact your energy supplier. They will work with you to find a payment plan you can afford. In addition, you may be eligible for federal assistance paying your bill.
Eat enough fat! This will keep your thyroid and metabolism functioning properly, and you'll stay much warmer.
Fill a large pot with water and let it simmer. The rising steam will keep your house amazingly warm.
Take a hot shower or bath and use oil or lotion on your skin when you get out. It's almost like putting on another thin layer of clothing.
Leave the warm water in the bathtub. It's like having a 25-40 gallon hot water bottle in your house.
Put on a hat. About 80% of your body heat is lost from the top of your head. If you're cold at night, wear it to bed.
Use a hot water bottle. Great for warming your hands & lap while sitting; also put it under the covers at the foot of the bed. Ahhh!
If the air is too cold when you're trying to sleep, consider rigging a makeshift cloth "tent" over your bed. Your own breathing will warm up the inside of the tent very quickly. There's a good reason those antique beds had roofs and curtains...
Use a humidifier. The added moisture in the air can increase the apparent temperature of your home by as much as 15 degrees.
Turn on the lights. Incandescent and halogen bulbs create light through heat and can significantly increase temperatures in a room.
Use a candle heater. It doesn't create as much heat as a fireplace or real heater, but will create warmth very cheaply.
Take advantage of solar energy; place a dark rug in sunny areas of your house during the day to absorb the sun's heat.
Place short fans set to their lowest settings so that they blow across radiant style heaters to circulate the warm air away from the heater, allowing the heater to warm new air.
Microwave socks or small homemade "pillows" filled with rice, dried corn, or beans for one minute in the microwave and use as a heating pad or bed-warmer (if you don't have a microwave, use a hot water bottle).
If you can afford it, leave other heat-producing appliances on, such as computers/monitors or strong lamps.
Vent your electric dryer back into your house.
After cooking, leave the oven door open to let the heat escape and warm up the area of the room around it.

Warnings

Be sure to remove any home-made or store bought "pillow" style heating pads from the bed before falling asleep. They retain heat for a long period of time and if left too often in one spot, they can heat feather blankets or mattress covers to a dangerous degree and cause fire.
Don't start any kind of fire or use your stove to stay warm, except for ovens that are approved by authorities, such as the fire department.
Do not use unapproved materials for safely covering registers. (Call your local hardware store for safe covers). The material could potentially heat up and start a fire.
Be aware that the more you seal off air circulation to the outside, you increase the possibility of a dangerous buildup of carbon monoxide in the air -- especially if you use natural gas or propane in the home. Be sure to install a carbon monoxide detector if you don't have one already. If you do, be sure to test it on a regular basis.
Devices that produce heat as a by-product of their main function, such as incandescent bulbs, stoves and computers, will be less efficient and more expensive than appliances designed for space heating.
Heating methods that increase air moisture (bathtub, humidifier) might encourage mold growth and condensation damage. Regularly check behind furniture that's standing against outside-facing walls, and around windows.