I just purchased a new Kindle Touch 3G and started to use immediately. I looked for an option to view files in landscape mode instead of portrait mode, but I couldn't find anything. But wait, I am sure there is such an option in an older model Kindle belongs to a friend. Then I came up to a post on CNET:
Amazon has updated the firmware for the Kindle Touch to version 5.1 and it actually has a few significant feature enhancements, including one that a lot of folks have been clamoring for: a landscape reading mode.
Great. I grabbed the hint. Then I visited the Kindle Touch Software Updates page. Reading the page, I noticed that my firmware version is very old :) So, updated the firmware as the site instructs and now I have landscape mode. Update operation is very easy if you obey the instructions.