If you have a Kindle or a Nook, here are two sites that will save you money. Amazon, BookLending.com and Ebookfling.com allow you to borrow books for free and loan yours out to others.
These ebook lending/borrowing sites are just like taking a trip to the library without using an ounce of gas to get there.
Amazon also offers plenty of free ebooks here that you can keep.
If you don’t have a Kindle, download the free app to your Mac, PC, Blackberry, Android, iPhone or iPad.
eBookFling: Borrow from others and share your Nook and Kindle ebooks with 14-day lending/borrowing privileges.
BookLending.com: This site allows you to borrow and lend Kindle books. You can register on the site or through Facebook Connect. There is a 14 day period to borrow a book.
Read all of the specifics on both sites to see which option (or both!) is good for you. Happy reading!