I don’t know how long this offer will be available, but I just got an IFTTT alert about a free version of English Standard Version, which is a decent translation.
It’s Protestant, and thus incomplete, which is bad. But it’s free, which is good. The readers are … variable: some fine, some … eh.
UPDATE: As Victor points out in the comments, you can also get King James (Old and New), New Revised Standard (Old and New), and Contemporary English Version (Old and New), as well as Bibles in various language. All free, for now.
For all languages, click here.