I'll probably repeat some a few others have posted, but here goes:
turn down your water heater
put on warmer clothes or put on cooler clothes rather than cranking the heater or a/c
use your windows and window coverings to your advantage- when you want it warmer, let the sun shine in; cooler, block that sun out
take shorter showers; even try for 'navy showers', where you only run the water to get wet then rinse when you are done, turn faucet off otherwise
hang your laundry dry; outside when you can (sun helps keep whites bright!), inside otherwise
don't use disposable diapers; cloth diaper (making sure you hang them to dry)
don't use artificial baby milk; breastfeed
soak super dirty or stained laundry for a period before the wash cycle vs. running the items through multiple cycles
always have water and snacks with you when you venture out; pack a meal if you know you'll be out at that time
clothing- shop discount stores. Most of the clothing is still high-quality, looks nice and lasts. Care for it gently- wash stains out asap, use the coolest water you can, line dry. Have 'play clothes' for children that you don't mind them really thrashing, and separate 'nice clothes' for situations that warrant it. Wear clothes until they truly need to be washed; hang on a peg and wear again.
try to use up all the food in your pantry and refrig vs. buying more groceries (or going out to eat); see how long you can go
remind yourself how much money you are saving while doing any particular frugal thing. ex: think of how much you are NOT spending on fast or other restaurant food when you pack a lunch.
eat leftovers; plan leftovers so you are cooking once for several meals
have more meatless meals
turn off lights, tv, etc., when not in the room
use the library- for books, cds, dvds, magazines, storytimes, family entertainment. I especially like that I can "try before I buy"- occassionally I'll think I want a cd, but most often, after checking it out, decide I would have wasted my money had I purchased
shop or at least comparison shop online- watch out for and figure in shipping, though! However, also factor in fuel (and time) if you are torn between ordering online and paying shipping vs. driving across town to buy locally.
if you use propane or heating oil, buy in the summer when prices are lower
have a budget; keep close track of every dollar, even penny, for a month or so
ok, maybe I'll stop now; just having fun brainstorming!