While not that aesthetically pleasing, the plastic window covers that you tape on and blow-heat taught really do help with leakage from windows.

1. Block drafts coming through your windows and doors using an inexpensive and simple-to-apply weatherstrip, such as this one from Home Depot: http://www.homedepot.com/Tools-Hardware-Hardware-Fasteners-Weather-Stripping/h_d1/N-5yc1vZ1xqdZard7/R-100047977/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

2. Hang double-layer, insulating curtains. We have these form Bed Bath & Beyond and they work great in our bedroom (100+ year old brownstone in Brooklyn): http://www.bedbathandbeyond.com/product.asp?SKU=110337&COL=279&RN=2138&

3. During the day when it's sunny out, open you shades & blinds to let the sun's natural warmth in. Close the blinds and shades when it gets dark in order to retain your home's warmth overnight.

4. Put down some extra rugs, wear slippers indoors, and have plenty of throws scattered around the house to cuddle in when you feel chilly.

smencher is a heat-conserving genius. I'm only adding:

1. Insulate your outlets - super easy to do, and inexpensive: http://dinogy.com/entry/31/energy-savings-tip-insulate-your-outlets

2. Space heaters are fantastic.

3. In addition to weather stripping the windows, consider a new round of caulk.

4. Don't wear the flannel pjs to bed. I know this one sounds counter-intuitive, but try it.

Best of luck!

1.If you have south facing windows, follow all the above instructions, particularly the ones about letting the sun in during the day and insulating at night. Take a look at the landscaping, if trees and shrubs are blocking the sun from warming the house, can you trim them? This is particularly important if you have external uninsulated masonry or stone walls. Another landscaping trick is to put in a large shallow pond (a kiddie pool?) strategically located to reflect more sunshine through your windows.
To increase the benefit of #1, increase thermal mass in the house, it soaks up heat during the day and releases it during the night. Even if it isn't in the sun it will still help buffer temp extremes. Here are some methods for accomplishing this as well as some more ideas for saving the heat you collect or generate.
2. Build shelves out of recycled stone, brick or cinder block. Fill the shelves with lots of large indoor plants in clay pots (keep the watering can full and in a sunny spot).
3. Build a table out of large full water barrels, painted black if they are in the sun (verify that the floor can support the weight).
4. Cover your floor with an insulation layer and lay down some ceramic tiles or concrete pavers (mortar is not necessary).
5. When you are caulking around windows and such take the time to remove the floor trim and caulk around the floor to wall joints. Insulate under the floor and attic as well depending on your budget and planned length of stay (this will depend on your location, insulation is not that expensive and with really high heating bills will pay for itself, try working a deal with your landlord, perhaps he could pay for it if you install).
6. If there is a fireplace, block it up! They suck cold air into a house and send most of the heat up the chimney.
7. Pay careful attention to prevailing winds. Don't use an entry/exit door that is exposed to the cold wind, go around to another door.
8. If there is a mudroom or glassed in porch use it like a vestibule. Make sure the interior door is always closed when the exterior door is open.
9. Study the ventilation in the house and reduce heat loss by limiting flow but don't sacrifice good indoor air quality (the plants will help there).
10. This may sound obvious but I am surprised at how often I've seen folks standing at the door chatting away while the door is open. Step outside and close the door!
11. Plan your cooking when you are going to be there to gain the benefit of the heat it generates, particularly use of the oven.
12. Install a programmable digital thermostat, they are not that expensive if you DIY it. Once you have it set, try not to override it to compensate for temporary personal temperature issues. And speaking of personal heat.
13. Exercise at home, the heat you generate might as well go to heat your house. At rest we generate about as much heat as a 100W incandescent light bulb, this goes way up when we get active.
14. Unless you have moisture issues try to shower at home as well, it is a good way to warm up for the evening or before bed. With most central heat the air will be too dry anyway so a hot shower will help to add moisture to the air (moist air holds more heat) and again why not generate the heat at home. Perhaps the money you save by not needing a gym membership anymore will pay for some of the above improvements.
15. Sleep with a friend, human or otherwise. It is surprising how warm a cat or dog will keep you in the night, another human even more so.

Oh, and wear a hat! A stylish one that matches your eyes. See #15.

Hi Leeny,
I'm in a similar situation myself.

We always cover our windows with the plastic window insulation. It's not very green, but it does save us a lot of money on heating.

Another great idea is window coverings. If you have a very drafty window (or a single-pane window), make sure it has not one but two curtains over it. Ideally there'd be a bit of an air pocket between the curtains (or a curtain and a blind). You can get insulating curtains, but they are expensive. We used two layers (a blind in the window frame and a curtain over it). Note that the curtains should completely cover the window and its sash.

Our new place has two french doors - so we'll be heavily relying on the plastic insulation this year. I'm looking into getting blinds or a second set of drapes for them.

This weekend I'm taking a lit incense stick and walking around the house to try and find the drafts. I'll insulate any electric plates or add caulk to any window or door trims that blow the smoke around. I suggest you try the same as it should give you some idea of the areas that should be addressed before the snow flies.

Back when I had drafty balcony doors - we covered the door with a blanket (taped in place) and filled the void between the door and the screen door with more blankets ( bundled up so it fills the entire gap). The door was warmer than the surrounding wall. :D We lost use of the window in the door, but we didn't miss it.

Another thing I have to do this year is buy a door sweep and insulating strips for my front door. It leads into a shared hallway; so the door sweep and insulating strips should block noise as well as cold air.

We occasionally use a space heater to heat the area we'll be in for a considerable amount of time (the TV room or the office for example). We've found it to be cheaper than trying to keep the whole house warm. It also works to help keep guests who are use to a warmer house comfortable.

Lastly, we add an extra comforter and blankets on the bed and keep slippers nearby.

Hope this helps.

Insulated curtains, or make your own window quilts. Google them. They can look like art, or just plain quilts. Roll up or draw back styles. Lots of great ideas already posted about weatherization. Good luck. We like toasty!