I have a lot of my resources online, but I'm finding that I can really absorb information from books in a different, maybe better, way than I can online. If you stack all the books that I'm reading right now on top of each other, it's a pretty big pile:
CSS : The Definitive Guide - Fantastic reference book, essential. I learned CSS by just determined hacking and reading the specs last year, and I wish I would have got this book before all that pain and struggle. Reading the XHTML/CSS spec is cool, but you will save yourself much pain by reading this book first.
JavaScript: The Definitive Guide - Amazing book, it paid for itself in about the first 2 hours of reading. Is really the definitive guide to Javascript, starts off with all the basics, and then gets into the really hairy stuff. Has some great reference chapters, essential.
Programming Ruby: The Pragmatic Programmers' Guide, Second Edition - Ruby is a totally awesome language, you can learn it really well off the web, but it's nice to have this book to peruse on the couch to learn really complex things like blocks and closures.
and I just ordered:
MySQL : Paul Dubois
