Having been involved in music in one form or another most of my life, I was really excited when tablets came into widespread usage and I finally had a really mobile and low profile way to handle sheet music! As a piano player (or any other musician) it can get cumbersome to lug around huge books and binders filled with music. Below are my picks for music notation apps. There are quite a few of them out there, and it could be that these don't fit your needs, but it's a good place to start!
A great way to organize all those uke club books in pdf that you collect!
Dropbox account you can also sync your tunes across devices - also cool. Songbook is available for Android, iOS and Windows.