If you do need to replace the furnace or windows, there are energy tax credits available on materials, not installation, until the end of the year. I've already written volumes about these credits. Just click on http://energytaxincentives.org and you'll find just about everything you'll need to know.
More energy-savings tips. Energy prices are rising about as fast as consumers can reduce consumption, so the goal is to be a little ahead of the utility bills.
The Alliance to Save Energy offers some energy-saving tips tailored to the depth of winter.
Conduct a "draft check." Your heating dollars could be going out your windows, doors, and electrical outlets. Check for air leaks throughout your home; look around doors, windows, fixtures, electrical outlets, wiring, plumbing, and fireplace dampers. Turn it into a family activity. Draft-proofing is the least expensive energy-efficiency investment with the biggest payoff.
Plug those air leaks. Seal leaks between doors or windows (and their frames) with weather stripping and between window frames and walls with sealant or caulk.
Install door sweeps on the insides of exterior doors. Cold air can seep in under doors. Solution: Door sweeps are cheap and keep the draft out. No sweeps available? Even a rolled-up towel or blanket will help. And consider twin or dual draft guards on both sides of doors where you feel drafts.
Open curtains and other window treatments on your west- and south-facing windows during the day to allow sunlight to naturally heat your home, and close them at night to make it harder for warm air to escape. If you are purchasing new drapes, consider an insulated lining, which reduces both heating and cooling bills.