Lettuce, Bok Choy and cabbage are relatively easy to grow from scraps. Instead of throwing out those leftover leaves, simply place them in a bowl with just a bit of water in the bottom. Keep the bowl somewhere that gets good sunlight and mist the leaves with water a couple of times each week. After 3 or 4 days, you will notice roots beginning to appear along with new leaves. When this happens you can transplant your lettuce or cabbage in soil.
Celery is one of the easiest foods to grow from leftover scraps. Just cut off the bottom or base of your celery and lay it in a bowl with just a bit of warm water in the bottom. Keep the bowl in direct sunlight as long as possible each day and after about a week, you will begin to see the leaves thickening and growing along the base. When this happens, you can transplant your celery in soil and wait for it to grow to full length.
If you love using lemongrass but have a difficult time finding it, simply regrow your own. Lemongrass will grow just like regular grass. You just place the root that is leftover in a glass bowl or jar with enough water to cover it and leave it in the sunlight. After about a week, you will notice new growth and when this happens you can transplant your lemongrass in a pot or in your herb garden.
If you love cooking with bean sprouts you can grow them yourself as well. You just need to soak a tablespoon or so of the beans that you want to grow in a jar with shallow water. Leave this overnight and in the morning, drain the water off and put the beans back in the container. Cover the container with a towel overnight and rinse them the next morning. Keep doing this until you notice the sprouts begin to appear and then until they reach the size that you want. This works well with mung beans and wheat berries.