I cut up an old fitted flannel sheet that we would never use again (DH says flannel makes him uncomfortably hot at night) and turned it into "pee towels." Now I use them for "number ones," and stick to the old California maxim, "if it's yellow, let it mellow; if it's brown, flush it down." It's working great and we are saving so much on buying toilet paper!
I get most of our household items (cookware, decorative items, clothing, etc.) from Goodwill. It's a good cause, it keeps stuff out of the landfill, and it's an inexpensive way to have good quality things at a fraction of the price.
We bought our last three cars (sequentially--we became a one-car household nine years ago) on eBay. Not particularly radical, but it scared a number of our friends and family members. All the cars worked out just great for us. Older cars keep the registration fees down, and as time marches, the better old cars become in comparison to the ones that are even older! For example, our current car is 13 years old, but it has power locks and windows, heated seats, auto-adjustable seats with "memory," a CD player, and so on. Hardly a hardship!
We gave up spending money to buy and maintain equipment for hobbies we rarely participate in. In my husband's case, it was golf. Then we got rid of our camping stuff. We did it a few times, and finally DH said, "why are we spending money to go out and pretend we are homeless?" We switched to bowling...much cheaper and a lot more fun!