There is a number of hacks and tools for Kindle that extend it’s functionality beyond what Amazon initially provided. This page attempts to summarize as many of these as possible.
|Name||Description||Kindle 1||Kindle 2||Kindle DX|
|Unicode Font Hack||Adds support for non-Latin languages (Cyrillic, Japanese, etc). You can read books in these languages once this hack is installed. Supports Kindle 2 (K2) and Kindle DX. For original Kindle (K1) different hack is required||Separate||Yes||Yes|
|Screensaver Hack||Allows replacing default screensaver images (authors) with images of your own choosing that can be dynamically added or removed from user-accessible portion of Kindle flash memory (USB drive)||Yes||Yes||Yes|
|Savory||Adds native support for DRM-free ePub and PDF files by installing Calibre converter on Kindle device itself. Also unlocks downloading of these file types from built-in Kindle browser.||No||Yes||No|
|PDF Download||Unlocks downloading of PDFs in built-in Kindle browser.||N/A||N/A||Yes|
|EBook Text Formatter||Fixes formatting and encoding of text files downloaded from the Internet by restoring proper paragraph breaks and getting rid of HTML markup and excessive space characters. Mainly designed with lib.ru in mind but may work for other text files and languages. Can also be used for Sony PRS-500 and PRS-505. This is a command-line Windows tool and it doesn’t modify Kindle in any way. You will need to install unicode font hack to enable display of non-Latin characters.||Yes||Yes||Yes|
Let me know if you find a hack that is not listed here or if some information becomes outdated.