I’ve published the script that I’ve been using personally for quite some time to make plain text files that were preformatted to specific page width nicely reflowable on Kindle and other eBook readers (I’ve tested it with Sony PRS-505). It can also strip any HTML tags and convert between character encodings.
This should make downloading books from websites like lib.ru and gutenberg.org easier for some for some people. More information about how to use the tool as well as download link can be found here.
I’ve also created a summary page for all Kindle hacks and tools that I currently know of. Feel free to let me know if some information needs to be added to updated.