In the process of learning 
Apache Struts for a large project at work, I have discovered 
Safari.  This online bookshelf, created by O'Reilly and some other technical book vendors, allows me to checkout books to be read in a web browser instead of having to buy stacks of paper books.
            
 
                        
I seem to be in the minority of preferring to read online and not on paper, but I find this to be an incredible site for me.  I tend to devour technical books for a month or two, then never look at them again; the Safari Bookshelf is ideally suited to this usage pattern.  
I can also read the books I have on my bookshelf anywhere I have web access without having to haul a couple hundred pages of paper around.  This was my other problem with paper books, I never had the one I needed for the project I was working on at the moment.  
I have seen a few discussions online along the lines of what's the point, this type of material can be found with a Google search.  I find that this is true for reference material, but information on the web is lacking on important matters like basic concepts and good initial learning resources.