Originally Posted by Zeebra
You can always "side load" kindle content to your iphone/iPad through itunes. Go to the App tab in iTunes when you have your iPhone/iPad plugged in, select the Kindle app under "File Sharing" at the bottom and drag your kindle files into the "Kindle Documents" window. They appear in your Kindle app.
Yes, this is the 'official' way of side-loading content, and the only way I would expect it to work (and the only scenario I would expect Amazon to test). If you bypass iTunes (use iPhone Explorer etc.), you are on your own, just be grateful when it happens to work. Doesn't calibre also expect you to use app file sharing via iTunes?
Been awhile since I side loaded anything, I just use PDS or send via email attachment or dropbox. I gather iOS5 has wireless sync to iTunes, but haven't tried that yet. I rarely have any need to launch iTunes, which is the way I like it...