One of my favorite iPhone apps is simply named Bible and is created by YouVersion.com. It is exactly what you would imagine - a Bible. I really like it because of a few other features also included.
Like any good digital Bible, it comes with an astounding number of translations. A few of them are even downloadable so you can read anywhere. Unfortunately, the NIV, my preference, isn't available to download, but steaming (can I use that word for text?) happens fast enough that it isn't an issue.
Another feature all good digital Bibles should have is the ability to search. I remember I being in a Bible study going through Revelations and we were trying to remember where a certain passage was located. Everyone started flipping their pages and I tapped on the search tab. Seconds later I found the exact verse we were looking for. This is indeed a very nice feature.
I saved the best for last. Our church is currently going through the Life Journal reading plan. It's a year-long plan that goes all the way through the Old Testament and through the New Testament twice. The Bible app offers this reading plan plus loads of others. I even had the choice to set my own speed, like say, take two years instead of one. It's been great to wake up in the morning and tap straight to today's reading plan (ha! pun intended!).
So, that's the Bible app. It's pretty straight forward, and has a few nice features. I wish it had some additional options, like linking to a Concordia or explanations of verses like a study Bible. Still, it's very useful and easy to use.