I bought a nice office chair at goodwill for $10. It rolls, swivels and has adjustable height. I've see them redone with nice fabric and plastic paint. I see the smaller ones for $5 at goodwill often.
Like this:
http://www.sugarbeecrafts.com/2008/0...oom-chair.html
And this is super awesome:
http://www.howjoyful.com/2011/08/des...ransformation/