If you want online ebooks only, the two e-book collections below are your best bets for business books. But there are others! And all e-book titles are fully catalogued and included in MARQCAT, too.
Google Books is a great resource for finding books and gives a preview of what the book is about and often short sections to view.
There is a link to see if your local library library owns the book and you can see if any of the local libraries have the book!