Aldi/markets for shopping: I avoid Coles/Woolworths.
Cook things from scratch: I make my own sauces, cakes, savory slices, muesli bars, popcorn and avoid pre-packaged junk as much as possible. DH makes his own ginger beer.
Grow herbs/vegies in our garden (not a big garden, we live in suburbia)
DS rarely gets new toys unless it's his birthday/Christmas. I'm always amazed by how much stuff other kids have compared to him, but honestly he doesn't miss it. He's just spent almost an hour with a water spray bottle doing 'graffiti' on the ground.
Make the most of local parks/libraries and hanging out with friends.
eBay for purchasing clothes/gifts. I barely ever by myself new clothes from the shops, I buy the majority of my clothes on eBay. They are all either new or near new for a fraction of the cost (and we are talking good quality well-know brands too)
I've been a SAHM on and off for 4 years and this is what has worked for us. Having said that we've just got the one kid so I guess that's made it easier too.
I'm about to go back to work full-time but I'm hoping these habits won't change too much. I'd rather put my salary aside as much as possible in order to save more money for good holidays (we haven't had any huge holidays in the last few years, mainly just road trips so that's been another saving!)