Oh my, I could go nuts on a question like this! I just finished reading a 50+ page thread on another chat board about this very topic. Here are some of the ones I remember:
use used dryer sheets to clean shower doors (tried it & it REALLY works!)
vinegar as a fabric softener (I also use dryer balls too)
vinegar as jet dry in the dishwasher
vinegar as a daily shower spray
home made cleaners
wash laundry in cold water
dry laundry on rack placed over heat vent (dries clothes, adds humidity to air)
actually eat all your left overs instead of throwing them away
no paper napkins
less use of paper towels
plastic glasses in the bathroom instead of paper cups
recycle as much as possible to cut down on garbage bags
manual mower to save gas/oil
CFL bulbs
power strips to shut things off and avoid phantom power drain
water saving shower heads and faucet aerators
coupons & hot coupon world for advance notice on sales
The Coupon Master to get extra coupons when needed
CVS, CVS, CVS!
home made detangler for my daughter's hair
use toaster oven instead of regular oven whenever necessary
use reward cards to earn cash
actually complete rebates when they are offered
using blankets, wearing sweats to keep warm with a lowered house temp
use restaurant.com to help lower the cost of the occasional meal out
That's all for now, my head hurts :-)