http://eloquentjavascript.net/ - HTML version has interactive console to practice exercises

http://javascript.infogami.com/Javascript_in_Ten_Minutes

http://yuiblog.com/crockford/

http://javascript.crockford.com/

More advanced:

http://www.addyosmani.com/resources/essentialjsdesignpattern...

http://bonsaiden.github.com/JavaScript-Garden/