I've been researching the different formats that different e-readers support. The formats determine how one's e-book is displayed on their e-readers. For instance, my nookcolor supports epub, pdf, and even powerpoint formats. Some word documents can also be displayed on my device. While I was looking up the kindle formats I found that the kindle only supports kindle format books, which is definitely a setback on answering my inquiry question. Devices like the iPad can support most of the ebook formats through the Kindle and Nook applications that are available for download on Apple's application market.
Scott Marlowe is a relatively new author and has his own blog. One of his posts talks all about ebook formats.
Personally my favorite format are the Epub files. I feel that Epub format most closely resembles actual books, as well as being fairly easy to convert into. I have a program called Calibre ebook management that converts files such as pdfs into epub that can easily be transferred to my device.