Instead of buying up a series of miniature clay pots in which to grow your seedlings, you can save money by growing them in something you were going to throw away anyway. Eggshells make great miniature planters, and they transfer easily to outdoor gardens when the plants inside have grown large enough. As long as you're pretty good with cracking an egg, you can set up a dozen planters in no time.
Get out a bowl to crack an egg into. Grab a fresh egg with your dominant hand and carefully crack it on the side of the bowl, striking the corner of the bowl near the narrow end of the egg. The goal is to break off the top third or so of the egg, leaving the bottom two thirds with the wide end intact. Empty the egg's contents into a bowl. If you plan on planting in multiple eggs, crack as many as desired.
Rinse out the eggshells, being careful not to crack them further.
Carefully poke a small drainage hole in the bottom of each eggshell using a push pin, tack or sewing needle. The drainage hole should be slightly bigger in diameter than the pin or needle, so you may need to use the point of your poking utensil to widen the hole a bit.
Use the same poking utensil to poke several holes in the bottom of an egg compartment in an egg carton. If you're preparing multiple eggshells, poke holes in as many egg compartments as necessary.
Place the eggshells into the prepared compartments of the egg carton. Set the egg carton into a shallow dish.
Fill each eggshell most of the way with potting soil.
Add a seed to each eggshell. Add a small amount of water to each one, as well.
Keep the egg planter indoors in a cool, sunny place and water the eggshells regularly until they begin to sprout.
Use your hands to dig a small hole in your outdoor garden for each sprouted eggshell. Plant each seedling by setting an egg in a hole and gently applying pressure to the shell with your fingers until it breaks apart in several places. When each shell is crushed, fill in the rest of the hole with a thin layer of soil.
Water and care for each seedling on a regular basis to see it through to maturity.