Another thing I like to do when I have nothing to do is to recreate recognizable icons. I like to see how closely I can approximate the original look, and often I can find new ways of using the tools available to me in Illustrator.
The Finder icon. This was simple really. Just something fun to do.
The QuickTime 7 icon. I made this one to practice using blend modes on gradients more effectively.
The new QuickTime X logo gave me an opportunity to use radial gradients, and customize their shape and placement.
The iChat icon let me try doing some more gradient blending modes, like the QuickTime 7 icon.