I just checked, and
www.gutenberg.com is also now working from the Kindle Keyboard with no computer required.
Of course it is easier to use
http://m.gutenberg.org/.
When this thread first opened, neither site was working for Kindle Keyboard downloads. Somebody has to have fixed something.
To review what this means: If you have a Kindle Keyboard 3G, you can, almost anywhere in the world, regardless of WiFi availability, download for free, from gutenberg.com, most halfway popular books if they were published before 1923. And when in a life + 50 country like Canada, New Zealand, Korea, Japan, China, and dozens of others, you can legally download the best books by authors who died before 1963 via gutenberg.ca and mobileread.mobi. My non-lawyer understanding is that you can then, legally, take your eReader, complete with new downloads, to home countries with long copyright periods such as the US and UK. This is part of what makes me a great enthusiast for the Kindle Keyboard 3G. I wouldn't give that up for a better lit screen.