To begin with, I stopped using Ziploc bags almost entirely. No more little sandwich bags, either - Tupperware instead. I still use super-large ones sometimes, mostly for freezing bread products, but when they're empty, I reuse them. I try to buy items in glass containers rather than plastic ones (though sometimes, the plastic price overrides the glass one).
I don't get plastic bags at the store anymore, either. I take reusable cloth bags with me. One day, I had to get a plastic bag at a department store (Spousal Unit and I were wandering to other stores), and I felt so guilty about it that I came home and made plarn.
Plarn is plastic yarn, made out of old plastic bags. It's easy to make, and though I haven't crafted with it yet, there are many projects you can make it into.
To create your own plarn, cut off one handle on the bag. Cut off the second handle at the base on one side (it will still be attached on the other side). Begin cutting all the way around the bag, creating a thin strip of plastic that is about an even width all the way around.
The base is more tricky to cut, but it is possible to make one long piece of plastic from the entire bag.
When the whole bag is cut up, you can reattach that first handle you cut off - just like if you were attaching the ends of any other yarn.
Roll it up and voila! You have a ball of plarn waiting to be made into any number of projects, and that bag will at least serve more of a purpose before visiting the landfill.
Here's one cool project I found: a crocheted recycled plastic bag purse!
According to the website where I found this one, pink plastic bags are hard to come by. White are, of course, most popular, but your yarn color is decided entirely by which bags you cut up! I like the idea of making your own yarn and being more environmentally friendly.
You can find lists of things to make out of plarn all over the internet. Bags of all shapes and sizes are just one idea - you can also make rugs, baskets, hats with wide brims, coasters, and many more awesome things. Maybe you could even make curtains!
For more about how to use less plastic in your life, check out Plastic Free by Beth Terry. She has a website, too!