Here's my entry for the Crafty by Nature Contest over at Craftstylish.com. It's easy and simple. It's not horribly impressive, but did I mention that it's easy and simple? You'll need:
* empty tin cans, rinsed out
* old wool sweater(s)
* bedding plants (or seeds) and a little soil
* a pair of scissors
Toss the sweater(s) into the washing machine using hot water and the highest agitation setting. Since they are wool they will shrink and felt up. Then toss them in the dryer or let air dry. Cut tubes from the arms the same length as the cans. Pot the plants/seeds in the cans. (And probably you should nail a hole or two on the bottom for drainage, although I didn't.) Slip the sweater tube over the can. Instant windowsill garden (or pencil holder or vase if you don't like getting your hands dirty.)
BTW, you have until midnight tonight to enter the contest - let me know if you do!