Insulation for the loft, and cavity walls if you've got them.
Any draughts coming in your house? Windows not fitting right? Cold air coming through the letterbox? Worth fixing those before winter - insulation tape and letterbox covers are cheap.
Check taps aren't dripping. Thermostatic valves on all radiators so you can turn off/down heat in rooms you aren't in. Consider if your boiler is so old and inefficient that a new condensing one might be an idea.
Dishwasher on eco 50 degree setting which means it doesn't blow-dry, unless it's jam-packed when I use the auto setting (55 or 60 deg, and blowdries the dishes).
Washing machine - mainly use Ecover but mainly because my gynaecologist recommended it. Usually wash at 40, 30 if smallish load and not too dirty. Although think a regular hotter load might be an idea to avoid mould buildup as it's horrible to clean off.
Have enough plastic bags hanging around to keep me going for decades - only skanky ones in bins get replaced.
Have piles of hand-me-down reusable nappies from familybabies 1+2, and they're less hassle than I thought, so might be worth getting some second-hand to try on your 2YO? Even if you only used then half the time it could save a lot over the next year.
Hardly drive the car, so have 2 friends on the insurance too so it gets moved at least once a fortnight.
As you can tell I'm driven as much by cost as by wanting to be eco-friendly - although stuff like getting eco paint, holidaying by train, and ensuring junk goes on Freecycle or to recycling points are slighlty more costly than the less-eco option. Although train travel is so much more civilised than airports, so I don't mind paying a little more.