http://www.books24x7.com/ -Referenceware for Professionals
http://www.safaribooksonline.com/ - Safari Bookshelf
http://safari.oreilly.com/ - O'Reilly Safari Bookshelf (same as Above I think it is the original)</a>
Some online book libraries - should ask my boss to get us a subscription, seems like a stupid resource not to use considering the prices - that of reading text online (which I should get used to by now) in this library, compared with the price of actually buying a book, waiting for it to arrive and finding out that it isn't good enough (especially with the crazy prices charged for these books, especially in Israel)