Even if you don't drink soda from 2 liter bottles, you probably know someone who does. Don't let all those containers go to the landfill! There are so many uses for them that you may never throw one out again.
Plant waterer. You can buy those spikes to screw on to the top of them, but why not just poke a three or four small holes in the bottom of a bottle, bury it beside your plant and fill it from the top? Leave a couple of inches sticking up and put the lid back on loosely to allow for air to replace the dripped water but keep insects and dirt out of it.
The tops make excellent funnels for shop and garage uses and can be tossed after using, or saved for reuse. They also fit perfectly into the top of gallon milk or water jugs.
Bottoms can be used to grow plants on a windowsill or to start plants for the garden.
Cut the bottom off in the correct shape and use it as a scoop for pet food, outdoor bird seed and so on.
Cut a bottle in two in the center, fill the bottom with soil and add plants. Take the top and make four short cuts at even intervals, then water the soil and place the top on, squeezing gently to get it to fit down into the bottom part. This is a perfect little greenhouse that almost eliminates the need for water. Be careful about putting it in the sun, though, because the temperature will soar.
I even came across an ambitious project involving building a full size greenhouse from plastic soda bottles.
And then there's this bright idea: How to light a home with a plastic soda bottle and bleach
Makes me wish I'd saved more of those from former days!