One of the biggest landfill components these days are water bottles. Yes, it is great to drink water, but many bottled waters come from MUNICIPAL sources (Dasani & Aquafina have both said YES they bottle their water from FAUCETS). Others come from countries like Fiji, so far away that the energy it takes to bottle and ship the water makes it ecologically insane to drink a water that the natives do not drink!
So what can we do? Do what Dasani & Aquafina do, but better. Buy a filter for your faucet or buy a pitcher with a filter so that you can bottle your own water for a fraction of the cost and drink it out of a reusable container. Better yet, a NON-PLASTIC container so it will never taste of plastic or have the chemicals of the plastic leach into your drinking water from the heat of sitting in the heat of your car. I bought SIGG water bottles from Switzerland, which are the sturdiest, most fashionable (yes, you can be green and fashionable) and most well-made drinking containers. They NEVER taste like plastic, they are made to hold even acidic drinks like juices without corroding, and they have styles and colors to reflect your individual style! You can probably find them in your local outdoor gear shop like Adventure 16 or REI, if you can't find them locally, go online and order them. If you like a flavor with your water, buy the PUR water filter with the flavored water attachment (great for kids or people who don't like "plain" water).
Another great "green" thing to do to lessen our landfills and footprints on this planet is to get reusable grocery bags. Europeans have been doing this for decades since plastic is not a way of life there as it is here. Every store markets themselves with canvas or plastic carry bags bearing their logo. Some places here do that like Trader Joe's which has several styles of bags from wine bottle carriers to cold insulated bags. Nubius Organics has several beautiful grocery and carry all bags that will make you wonder why you ever settled for a plain generic plastic bag to carry your groceries.
If you want to read about the possibilities of living from "Cradle to Cradle", then buy the book of the same title and get inspired. The book is even printed on a material that is reusable!
Lessen your landfill contribution with just two simple things, a reusable water bottle and a reusable grocery bag. It's easy to be green!