I've been seeing these awesome moss terrariums on etsy.com and I love them. The problem is that I just can't justify paying $40 for a kit that contains about $9 of things, most of which I had around my house anyway.
Here's what you need:
Glass container with a lid (anywhere from Walmart to Hobby Lobby)
Activated Carbon (aquairum supply isle of most stores)
Rocks (I used what was left over out of a bag from the $1 store)
Moss (or clovers ro whatever you have growing around the tree out back) If you don't have moss out back ask your friends. It's pretty common and can even be found in parks if you live in the city. You don't need much and you don't have to dig a hole, just loosen it from the ground with a spoon or spade and pull it up.
This is so easy a child could do it. In fact, mine did. Layer the items like this: rocks on bottom, then carbon (keeps the smell away and stops fungus growth), soil is next and finally add the moss. Once everything is in like you'd like it to look wet it and put the top on. You can add cute things like clay mushrooms or little figures. Keep in indirect sunlight. Water only if it gets dry. TaDa!
You just saved enough money by doing it yourself to make a quick stop at the craft store. : )
Now I want to make a really cute one is a pretty apothecary jar for me. This one my little girl did for her room.