For the aspiring musician on a budget, or a seasoned pro looking to expand their music library, imslp is a wonderful resource. While there is some digging required, sifting through the vast amount of literature available is easy after navigating the site for a bit. IMSLP is a database of public domain music, offering different versions of pieces. The files are easily downloaded in the PDF format, enabling viewing from an array of devices, and most importantly the ability to print a physical copy.