Most 6 year olds like to run around and holler.
I wouldn't do too many competitive games since someone always ends up crying. I'm not of the school that 'everyone should win' in all games, but a party winds everyone up and emotions run high.
Pinatas are fun and they can hit it with a stick painted like a light saber; crafts are great if you want to organize them; and check out the web sites above.