There's good news, though. If you're a crafter, there are tons of ways you can use plastic bags. My favorite way is by making a plastic yarn out of it, usually called plarn. It's a simple process. I like making it while watching TV. Here's a great page that tells you how to make it.
Once you've got your plarn made, you can make just about anything you want with it. Truth be told, if you make the plarn thin enough, you can use it like you would any other kind of yarn. You probably don't want to make a sweater out of it, but I bet there are lots of cool patterns you already have that you can use.
Of course, in my searching, I found a bunch of awesome patterns made specifically with plarn in mind. And my favorites were the ones for useful, everyday items that save you from having to go out and buy. What better way to use your old bags than to make a new reusable market bag? Once you have a few bags made, you'll never have the problem of plastic bags again.
This crocheted plarn basket is useful and also really pretty, and it reuses another commonly tossed plastic item. Super cool idea? Recycled giftwrap plarn box is an awesome way to give gifts. Not only do your friends get a nice gift, they also get a neat little plarn box that they can either use in their house or use to give another gift.
Another cool idea is this plarn backpack, which not only is very pretty but will likely save you a bundle (backpacks are expensive!). Along those same lines is this plastique plarn purse, which is so unique and sharp looking that I wouldn't have guessed it was made out of plarn.
Here are handful of others I really liked: Clothes pin bag, Baseball cap, Water bottle holder, Pot scrubby, Round rug, Scrubby dish cloths.
Another option for plarn, if you don't know how to knit or crochet, is to weave it. Anyone can weave with the simplest of materials. Here's how to start on a cardboard loom. Weave small squares, and then stitch them together to make a rug or a bag.
For those of you less crafty in general, here is some simple, everyday uses for plastic bags:
1) Use them as trash can liners
2) Use plastic bags instead of packing peanuts when you ship
3) Wrap them around fragile items when moving or storing
4) Reuse as a grocery bag
5) Emergency rain hat
6) Cut and tack to shelves for a washable shelf liner
But the best way to cut down on the amount of plastic bags that you throw away is to start taking reusable market bags with you to the store. Keep them in your car at all times so that you're less likely to forget them.
PS, if any of you can't crochet or knit but you would love to have some of those items I posted, let me know! I'd be happy to make them for you.