Well, here are a few others I've done with my kids.

- Make little plant greenhouses out of empty plastic soda bottles. Cut the top off of the soda bottle, fill the bottom with soil, add seeds and water, then fit the bottle top back on. The kids don't have to be as consistent about keeping the seeds watered, as the environment stays moist, so it is a low-frustration way for them to start seeds.

- Make a bird feeder. This is a great project for empty plastic jars. You can turn a plastic peanut butter jar and a larger plastic jar lid into a bird feeder. Basically, the peanut butter jar is the hopper, and you bold the larger lid on the bottom of it as the seed tray that the birds eat from. cut a few holes in the bottom of the jar, so the seeds can spill out onto the tray. Add an I-hook to the top of the lid so you can hang it.

- Make a butterfly feeder. If you have a largish plastic dish that is no longer used, you can turn it into a butterfly feeder. We used an old garden pot saucer that I no longer needed. The children painted the outside of the saucer with a non-toxic bright paint. We poked holes in the rim and strung it with garden twine, so we could hang it. Then we made butterfly nectar and added mushy fruit and a brightly-colored plastic sponge for the butterflies to land on. You can hang it out when the rain stops.

- Bird nesting material box. Use an old suet holder. Fill it with short lengths of leftover yarn (6 inches or shorter, so the baby birds don't get tangled). Hang it outside for birds to grab for their nests. (Obviously, this one is for early spring.)