Since the Rebel posted his request for online Java tutorials, I've been thinking about collecting a similar resource, but for Java eBooks in PDF. Please use the comments or email me if you have links to other resources (and I'll be adding to this list as I discover them). Also, there are a variety of PDFs that can be found using Gnutella, but obviously I can't link to them here.
I think another great resource for eBooks online is O'Reilly's Safari. It's an awesome service that I use once or twice a month, but is more than worth it to me to keep paying every month just to have it available for me. If you're not signed up already, you definitely should think about it... There's A LOT of books on Safari, though, so I think maybe my next list will be "Safari Books That Don't Suck."
I have this dream of reading all my technical books someday on a small/light full-color tablet PC or some sort of eBook reader (with WiFi of course). The size of technical books are ridiculous. Buying a tablet PC is not happening any time soon for me due to budget reasons, but there's no reason not to prepare in advance.
Later: Thanks Lee Mun Liong!