Earlier this week Amazon launched an iPhone-friendly version of its website. When you go to Amazon.com in Safari on your iPhone or iPod Touch, it automatically gives you the iPhone version (and gives you the option of seeing the PC version, if you want). This is the whole Amazon site, not just the Kindle ebook area. If you do a search, you can, just like the desktop site, search any specific area of the site, or choose just to search the Kindle area. Confusingly, if you've used the site in the past to get books for your Kindle app, it seems to remember you. But if you want to do something other get ebooks from the Kindle area, such as look at your shopping cart, then you have to log in again to your regular Amazon account. You can also access the site from within the Kindle app by tapping Get Books in the Home screen.
I really like the iPhone Kindle app. The first thing I did was download a number of samples, thinking I'd just read the freebie portions and not spend the money to buy the book. But as you might expect, I got to the end of The Well Dressed Ape" and, having found it fascinating, couldn't resist clicking the Buy Now link. One click, and the book was mine.
Update 5/26/09: I recently noticed that there is also an Amazon Mobile app that let users of the iPhone and iPod Touch quickly search, shop, compare prices, read reviews, and make purchases on Amazon.com via a very simple interface.