The Kindle app is my favorite app for both iOS and Android. 
I say this for one simple reason: you can use it to read any document or article on any device. I have tried other e-reader and read later software. The best one I found was the Kindle app. The beauty is that this app turns your device into an e-reader without limitations. With a Kindle DX or Paperwhite, you are limited to reading, unless you jailbreak or root it. Not so when you use one of the Kindle apps. If you have an iPod with the Kindle app (like I have), you have all of the power of a Kindle e-reader plus access to a world of other apps and games. My point is that you can use a FREE app to turn your device into an e-reader instead of shelling out extra money.
Out of the box, the only way you can get documents into the Kindle app is to email them to an Amazon account. However,the file types that you are allowed to email are limited. To over come this limitation you can use a site called WappWolf to convert documents to a Kindle friendly format. You can configure WappWolf to monitor a DropBox folder. Once it detects a file it will convert it to a Kindle format and sent it to your Kindle.
Another great tool is called Klip.me.The Klip.Me extension for Chrome is the best extension I have found to send articles to Kindle from your browser. It works better then the official extension from Amazon, for some reason. The best extension that I found for Firefox is Push to Kindle.
To download the Kindle apps for iOS, Android and other, go here. Enjoy reading.
