I don't mind keeping full skeins of yarn around. You can make a lot of different things with one skein of yarn. It's the little balls I have left after a project that are hard to keep track of. They're always falling out of my yarn bins and rolling under dressers and tables.
My favorite way to use them up is to make little amigurumi figures. They take very little yarn, and they're so fun to play with. My favorite feature of amigurumi is the financial aspect. Making toys from leftover yarn is SO cheap. Remember when I made this Elmo for my son? I couldn't find a similar version for less than $20 at the store. I just used leftover yarn pieces, so he was pretty much free. Can't beat that.
Today, I wanted to get rid of little balls of black and gray yarn. I used a pattern found in Leisure Arts Easy Crochet Critters found here (I bought mine on Amazon, but they have them in craft stores), and made this little penguin.
I can tell he will fit right in here in our house. Look where I found him just minutes after I gave him feet.
A penguin after my own heart.
This little lady was something I made a few months ago. She comes from the same book of patterns too.