Amazon is running a special on 900+ Kindle ebooks including a number of religious books* through July 27, 2011. Remember that Kindle books can be read not only on a Kindle but also on Amazon's free Kindle apps for pc, mac, and most smart phones.
Among the deals you can find the NIV Bible for $3.99, the NIV Archaeological Study Bible for $2.99, How to Read the Bible for All Its Worth for $2.99, Bridges' The Pursuit of Holiness for $2.99, Beth Moore's When Godly People Do Ungodly Things for $2.99, and Strobel's The Case for Christ for $2.99 plus lots more.
I always encourage believers to read good books, and if you can get them cheap, so much the better. Take a look and see if there's something you can benefit from.
* Please be aware that page lists "religious" books, not Christian. There is sadly no way to further narrow down that list.