4 apps to keep you green in more ways than one

(MoneyWatch) Earth Day is a good reminder that we all can do things to improve the environment -- to be "green." And while being good to the place you call home is always a good idea, how much better is it to get two benefits for the price of one? To that end, here is a collection of apps that can make you more ecologically friendly while you also save some of the folding green in your wallet. And all the apps have both Apple (AAPL) iOS and Google (GOOG) Android versions.

Stop unwanted paper mail

PaperKarma is not only incredibly useful if you're tired of mountains of junk mail, but fiendishly clever. You use your smartphone or tablet to take a picture of the offending mail that identifies the sender. The app vendor, Readabl, sends a letter out to the organization, asking it to remove you from their mailing list.

Will it work every time? Maybe not, but why not try? The less junk mail you have to sort through and toss, the more time (which is worth money) you save. If you live in a community where you're charged for volume or weight of trash, this could further save a bit. Unfortunately, it doesn't work with companies that legitimately send you bills. Will the next version add that feature? We can only hope.

Recycle that trash

Speaking of reducing your trash volume, recycling can do wonders, particularly when you've got items that aren't supposed to go into a landfill or that you might get charged for disposal. The iRecycle app from website Earth911 will let you choose a category of recycling and, given a ZIP code or address, tell you the nearest locations that will take materials off your hands.

Split commuting costs

There is nothing new in the concept of carpooling. By having multiple people in a vehicle, each taking turns driving, you not only split the commuting cost for all, but you more efficiently use vehicles and reduce the carbon impact.

Avego simplifies the whole process. It looks for other users that might be a match for your route in real time, whether drivers or riders, calculates expenses of fuel and maintenance, and lets everyone know what they should be paying. And why stop at commuting? Heading to a mall? Maybe someone else it itching to save some money while heading off to do some shopping.

Public transit directions

Trying to navigate a city by mass transit can be tricky when you don't do it regularly. What is the right train or bus line to take and which stop gets you closest to your destination? HopStop does the hard work for you, with extensive information, like maps and schedules, and even step-by-step directions for getting from here to there.

In addition to the iPhone and Android phone apps, there is also a Web version so you can plan in advance from a tablet or PC.