Here's what I did when gas hit $2.00/gal a while back:

I started grocery shopping on the bicycle. OK,granting that I live by myself and don't have a family to shop for when I make the trip,it still saves a bunch of cash. Here's how I do it,and why it seems to work so well:

Forget the expensive bike saddlebags that are sized for one brown paper grocery bag apiece. Not that they don't work,but they're a hassle to keep balanced,and have been known to come completely off the bike right at the top of a speed bump. A couple of episodes of me running around in traffic picking up soup cans convinced me that there had to be a better way.

And there was. I took a plain old generic duffel bag and equipped it with a shoulder strap. Then I added a bootlace and a cheap carabiner to one of the end handles on the bag.

The shoulder strap goes over my shoulder and neck (bag sort of on my right,shoulder strap all the way over my head on the left shoulder,in my case. ) Then the carabiner that's tied onto the bootlace is yanked around my left side,and hooked into a beltloop just to the left of my zipper. The bootlace/carabiner is important,since that's what keeps the bag centered on your back when you're riding,instead of suddenly deciding to shift around and throw you off balance.

With a little bit of effort,I can carry a week's worth of groceries for me. And it's good for several reasons;

1)exercise. Plain old cardiovascular exercise is a great way to stay in shape,keep from getting sick,and all the other benefits associated with keeping the heart and lungs in good shape.

2)Saves fuel. You wouldn't think a 10 block round trip to the store uses as much gas as it does,but over a month's time,I can see a noticeable difference in the fuel bill.

3)The bicycle/duffle bag shopping method pretty much eliminates almost all impulse buying. I used to go shopping every week,and load up on a bunch of crap,and wound up throwing a significant amount in the garbage after it sat in the fridge for a month and turned an interesting color.

Not having a great deal of space or weight carrying ability while shopping using a bicycle has been a real money saver. I now make two trips a week,and buy what I know I'll need and use in the next two or three days. And once that duffel bag is full,that's it. If I want to get something that isn't on the list,well and good. BUT if I do that,I know that something has to be put back on the shelf. Amazing how much money this saves.,,

Not saying this is for everyone,but it works for me,and I most certainly intend to keep doing it!