I recommend "JavaScript: The Definitive Guide". I read a couple of pages in B&N to see if it was any good, and it paid for itself right there.
edit: Get the 5th Edition. See nickb's comment.
edit: Get the 5th Edition. See nickb's comment.
Also check out 'Pro Javacsript Techniques' by John Resig.
Read this article on closures which is the best description I have read of such a crucial crucial aspect of the language: http://jibbering.com/faq/faq_notes/closures.html
Also read Crockford: http://javascript.crockford.com/
I'd recommend that, and of course the Definitive Guide. Look for the Rhino.
Once you have learned javascript, DHTML: The Definitive Reference is a great desktop reference, although it's less important now that javascript libraries are so good.