My oldest went as a Ghost Pirate.
This was a easy costume: 1 single white sheet torn at the edges and then I added glow in the dark paint to them (edges). A little face paint and a hat I got at Kmart.
My baby went as a Mummy, because at the time he was learning to walk and would balance himself by having his arms out in front of him.
His costume was a little more difficult - I took a white tee (thrift store) and gauze, other white fabric and more white tees cut into strips. I sewed all these strips onto the tee and then tea died it all (also made a cap for him). Paired with a long sleeve shirt and dark sweats.
My husband was Cap't Kirk (Pirates of the Great Salt Lake - this is going to be a rather funny movie, you can see clips at http://www.piratesofthegreatsaltlake.com/freethepirates/index.html or http://www.piratesofthegreatsaltlake.com).
I hade to make his pirate hat (took a large circle of orange fabric - didn't have black and no money to buy any). I took a balloon to get the head part of the hat and then sewed it into pirate hat shape and painted black. We bought a belt buckle for $2 and I painted a skull and bones on it with metal paint, the rest of his costume came from the thrift store.
I went as Mother Nature and if you know me at all you would know that that was PERFECT!
I took a bed sheet and cut a hole in the center for my head, tore the edges and then sewed up the side which also made the sleeves. I took it outside and with watered down acrylics I sprayed on the color - I wanted it to have the look of the sky at the top and go down in color til it reached the ground (brown on the bottom torn edges). I bought some fake flowers and leaves and sewed them on - I added a little glitter paint to the costume too, to give it a fairy look. I finished the piece off with butterflies I made from polymer and I added brown ribbon and soft scarves to give it a wispiness.