For lovers of classical music, score-reading is an invaluable skill. It allows one to really dig into the inner details of a work, tracing themes and motifs through their development and studying just how a composer uses notes on paper to create stunning orchestral effects. I used to spend hours reading scores, and it's a part of my classical music hobby that I dearly wish to start up again.
The problem is, scores can be hard to track down, except for the few you might find at Borders or Barnes&Noble in the sheet music section (and the number of these has declined over the years, I've noticed). Well, Elibron seems to be a good source of music scores. I haven't bought anything from them (yet), and thus can't totally recommend them from a service standpoint, but it seems like a site worth exploring.