1. GoodGuide is an app that serves as a database of over 70,000 products you can find on store shelves, along with information on the environmental impacts they can make on the world around you. See a product at the store, look it up on the app, and then get information and ratings right there in the app about how the product affects your health, the environment, and society at large. It's an excellent tool for making good decisions about what you buy at the grocery store and elsewhere, and it's a free download for the iPhone or iPod touch.

2. Pollution is another free app that will inform you as to potential sources of pollutants in your area. It features an interactive map, on which you can see local pollutant sources, as well as information about what kinds of impact they're having and the types of emissions and quantity that the various sources are contributing to the world around you. It's not a perfect resource (tracking every single source of electromagnetic, air, water, and ground pollution is extremely hard, and though the database is updated often, the situation can change quickly), but it should give you a good idea of just where the trouble spots are in your community.

3. Carbon Calc is one of the many (many -- as you might expect, the "green" trend has contributed to plenty of junk apps on the App Store) carbon calculators out there for the iPhone and the iPod touch. Still, though it's free, it looks good, it's easy to use, and though it is missing a few pieces of information about where your "carbon footprint" comes from (we all live in different places and in different ways, so this is hardly a "one app fits all" situation), it will tell you where you lie on the average scale, and maybe give you some food for thought about what you're doing right or could do differently. If you want more information about carbon footprints and how to change them, Blog Action Day recommends this writeup of the 15 best carbon calculators available on the web.

4. Fighting climate change isn't always about tightening the belt or eating granola -- sometimes it's just about being sensible and saving money, and that's something that, as our own Dave Caolo wrote, Gas Cubby will help you do in style (for a trial run with the product, you can get the 5-record version of Gas Cubby Lite). It'll help you track your car's miles per gallon and vehicle maintenance, show charts as to what's happening with your vehicle, and even send out reminders for periodic things you can do to keep your vehicle running well. That keeps money in your pocket, and using less gas to keep your car running longer helps us prevent fossil fuel usage and the wasting of other resources. Everybody wins!

5. Finally, one way you can help keep the earth clean is by getting your hands dirty: setting up a garden of your own, whether it's a tiny windowsill herb garden or a sprawling place to grow record-breaking pumpkins and tomatoes, not only gets you in touch with nature and how it all works, but saves you that trip to the grocery store when you just need a little basil or parsley for your cooking. Unfortunately, the choices for gardening apps on the store are pretty wilted -- either an app's great on interface but short on information (or vice versa -- would-be garden app designers take note!), but Pocket Garden is probably the best choice out right now. It's 99 cents, or free with ads, and it'll help you grow your own plants whether you're growing anything from Asparagus to Zucchini.

Obviously, messing around with an iPhone app won't help slow or even reverse climate change (and you're wasting your money on any app that claims it will). But the point of Blog Action Day is to spark awareness and discussion about this issue, and these apps can help you do just that.