Further to a discussion over a year ago about Stack Overflow portable edition, I've since got a Kindle and have been working on this project again.
I got a fast new machine with lots of disk space, installed 64-bit FreeBSD on it, and now I can mmap() the whole >4G
posts.xml file. That really helped to make this possible.
As a demonstration of what this can do, I've created an ebook (in Mobipocket format, compatible with the Kindle and hopefully everything else) of the SO questions with score 20 or more in each of the top 20 tags:
That page has some details about how the books are organised and how to navigate them (on the Kindle, anyway). Here's some screenshots (click to embiggen):
Source is on Github.