If you're looking for computer books I highly recommedn O'reilly's safari.oreilly.com
It's a heck of a lot cheaper if you just need a chapter or two, or want to investigate a new language. Alternatives are going to Border's/B&K but the coffee is expensive enough to pay for a small safari bookshelf

One thing I've noted over the years of using safari though is that nothing replaces holding the book, so I usually end up only using Safari for reference.