Despite it being a remarkable little device, one thing that annoys me about the Kindle is how the screensaver gets enabled whenever I leave it for more than a minute. One can only look at a portrait of Emily Dickinson so many times, you know? As far as I understand, there isn't much happening in the background on the Kindle when you are reading and the page is static, which is why it has such extraordinary battery life, and since my kindle rarely leaves my desk, I don't ever need the screensaver to kick in. This way, it's more like a book that I can put down and pick up right where I left off.

Since there are no settings to disable this you can resort to some hackery to disable the Kindle 3's screensaver:

• Go to the Homescreen
• Press the Enter key (looks like a return key with a little arrow)
• type ';debugOn' (note the capital 'O' and the semicolon in front)
• type '~disableScreensaver' (note the capital 'S' and the tilde in front)
• type ';debugOff' (again, note the capital 'O' and the semicolon in front)
• and to reenable the screensaver use instead '~resumeScreensaver'

I can't speak as to whether this works on other devices, but it works like a charm for the Kindle 3.
Happy reading!

Edit: On further testing, this appears to reduce your battery life quite a bit, use at your own discretion :(