I love using the Youversion Bible app. It is the app I go to most of the time.
I also like the Glo Bible. It has many nice features and links to the Youversion app. Glo is what I use to post my Bible notes during sermons and Bible studies. Another nice feature of Glo is that, for me at least, since I was one of the first users of Glo I still have access to the NIV 1984 edition text, which I greatly prefer to the latest NIV 2011 edition.