Bartleby.com is a must, only the coolest site ever invented for readers and writers. It features a mind-boggling slew of reference titles (we're talking hundreds), poetry anthologies, novels (the classics), and nonfiction titles. You can read anything from Roget's Thesaurus to Bartlett's Quotations to the King James Bible to Gray's Anatomy. Need some free Shakespeare fast? Bartleby.com has it. In fact, it probably has every reference title or classic work you can think of.
So bookmark it already!