I had watermelon, radish, and cantaloupe seeds I needed to start. It is a lot easier to start seeds in a sunny window inside, so I went looking for something to put them in. Pinterest had the answer... egg shells.
Just crack the eggs (I tried to crack them closer to the small end), RINSE THEM OUT (very important), add a little soil ( I used organic), and plant your seeds.
When they sprout and are ready to be moved outside, just crack the egg a little more and plant the whole thing.