[savinggreen]

first two are not very timely in my part of the world as they are for summer coolness.

1. get a cold air return installed in your basement (drop a duct down to floor level with a register) and run your furnace as a fan in the summer instead of air conditioning. this will circulate cold air from your basement through the rest of your house.
2. my friend calls this one "ghetto air conditioning". take a chunk of ice and stick it in a bowl in front of a fan. very cheap room air conditioning.
3. run ceiling fans in the winter, but do it in the right direction (if you think of the fan blades as a knife, then in the summer, they should be turning as though they're icing a cake, and in the winter, as though they're scraping the icing off the cake). This will help to circulate the warm air throughout the room, making it feel warmer. This is especially effective for rooms with high ceilings. For old homes without a cold air return on the 2nd floor, a ceiling fan above the stars can really help.
4. check the dampers on the ducts leaving your furnace. Often both a small and a large room have full-sized registers. In my house, this meant that my bathroom was a good 5 degrees warmer than the living room. Each duct running off the main should have some sort of lever to adjust the the level of dampening. I set mine to fully open for the main living space (living room, kitchen, office, dining room and bedrooms), and to half closed for the spare room and bathroom. I closed it entirely for the front hall.
5. not so creative, but check the temperature setting on your hot water heater. They are often WAY higher than they need to be.