From the Crossway blog:
When we released the English Standard Version of the Bible in 2001, we immediately made it available online, for free. Eager to get the Bible into as many formats as people will read, we’ve released the ESV as an iPhone/iPad app, Android app, and as an eBook for your Kindle or Nook.
Prefer to listen to Scripture? You can stream it at ESV Online. We’ve worked with our friends at Faith Comes By Hearing to offer several audio versions of the Bible, for free. Another set of audio files is available on YouTube.
For our technologically savvy friends, we’ve even made the API to our ESV Bible text and ESV audio available free of charge for non-commercial use.