The Kindle app for iPhone and iPad (free, universal) has been updated to version 2.9, giving iPad users access to the Kindle Fire's collection of more than 400 magazines and newspapers. You can buy individual issues or subscriptions, which will be delivered to the device when available. Note that the magazines and newspapers are limited to the iPad.
That doesn't mean there's nothing new for iPhone and iPod touch owners. You folks will be able to email documents to the app via a special email address and open PDFs from Mail or Safari.
The free update is available now. Have at it!