[Edit] The "~exec" hack works only on a small portion of the Kindle 3 that has some test files left over by Amazon. Otherwise you have to jailbreak the kindle to gain access to it: http://www.mobileread.com/forums/showthread.php?t=88004
a full reset takes longer than 15 seconds. for example, there are browser issues in the original K3 release to consumers that require a longer time between off/on to clear (like a few minutes I think to be safe- I know it is longer than 15 seconds though). Check the kindle forums below for additional detail.
pictures must be in a folder right under the /pictures folder that you have to manually create. you can't put them in the pictures folder or in a subfolder of a subfolder. you can have multiple groups of pictures by having them in different subfolders of /pictures folder, but that ends up cluttering up your menu, if you like having only a few things in it at a time.
mp3s can go into audible or music folder (have to manually create music).
mp3s in audible show up like books. mp3s in music can be played while browsing, reading, etc. via experimental in home menu.
PDFs can load slow as hell, and are a pain to have to resize (basically, they are not usable unless you have a big font in the PDF). Instead try to get free books from Amazon or in mobi format, which is the un-DRM'd version of the format Amazon uses for their books (AZW). Mobi format is available from Gutenberg as the what it calls the Kindle format.
Don't load up your Kindle with a ton of crap books because it is a pain in the butt to find the one you want. Unless absolutely necessary, you are probably better off keeping a small collection in it.
Pictures are in b/w so darker pictures are just usable, and this is just a "neat" feature, not likely to be used much. It might be neat for storing clear customized b/w blueprints, wireframe designs, simple electronic circuit design, simple workflows, etc. It is also kind of hard to resize so it makes good use of the screen (600px × 800px) but then you really want many rotated to look good right off the bat.
The browser sucks because it is buggy and because you can't zoom or click easily with the included controls. Buy a Kindle to read, not browse Facebook or type email. Once the Kindle has touch screen and pinch zoom and color, then the browser will be ok. No I'm not suggesting an iPad. They are too reflective in the sun and they aren't meant for reading, and they are overkill for an e-reader.
For the scoop on Kindles from a good broad section of its (not always super-technical) users that Amazon watches is here:
"Don't load up your Kindle with a ton of crap books because it is a pain in the butt to find the one you want. Unless absolutely necessary, you are probably better off keeping a small collection in it."
Now you can create folders to manage your books, which is a lot better.
For making PDFs readable: from the aA menu while looking at a PDF increase the contrast to maximum and then rotate it into landscape view. Hold your Kindle sideways and now the PDFs are readable.
It's not perfect, but I have found that I'd rather read vendor documentation like this on the Kindle than on the harsh black/white of my monitor.
The browser suck hard (from google news is impossible to open any link because "oepning multiple windows is not supported."), but the "Article Mode" is really good.
From what I understand, an E Ink screen doesn't consume power when simply keeping an image displayed. Instead, the battery of the Kindle is only diminished by WiFi and Whispernet use, page refreshes (turning pages, typing, navigating, etc.) and book indexing.*
If the above is true, I assume Standby merely prevents accidental key presses and does not help maintain the battery life, right? After all, you can still send books to your Kindle while it is in Standby mode.
The Kindle is effectively "off" in standby mode. You can't send books to it, unless you use a USB cable, in which case it boots up in USB mass storage mode. Or is wifi still on on the Kindle 3?
Funny, I send books to my Kindle wirelessly all the time in standby mode, and when I wake it, they're already there. Perhaps you're confusing standby (displaying an image, from either the ~4sec power button push or inactivity timeout) with the off setting (~15sec power button push).
Having sizable undocumented things like an Image Viewer and games lurking around bothers me a bit as it brings a sense of sloppiness to a great focused device.
http://www.mobileread.com/forums/showthread.php?t=97745
[Edit] The "~exec" hack works only on a small portion of the Kindle 3 that has some test files left over by Amazon. Otherwise you have to jailbreak the kindle to gain access to it: http://www.mobileread.com/forums/showthread.php?t=88004