EBL (EBook Library)
Ebook Library (EBL) is an online product delivering over 190,000 ebooks of all disciplines in a collection that grows by 1-2,000 new titles each month.  We have access to the whole catalogue.

EBL guide  

For Business & IT titles please check Safari Books Online first.

Safari Books Online
Safari Books Online provides access to an expansive digital collection of business and technical publications at your fingertips, available anytime, anywhere. Safari is the only service in the world that delivers entire searchable collections of books, working manuscripts, short topic PDFs, certification study guides, and instructional videos from top technology and business publishers. (around 5000 book titles available).

We currently subscribe to Safari Business Books and Safari IT books.
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Also, don't forget to check out Google Books - free online books via Google.
Right now, you can search the full text of some seven million books through Google Book Search. Try it out for yourself.