On August 19, 2009 why the lucky stiff removed every trace of his work from the Internet, including his Poignant Guide to Ruby.
I've salvaged what I could, cleaned it up a bit and saved here. He released the book under the Attribution-ShareAlike license. There's a Japanese translation of the book, although I can't tell how up to date it is.
Interesting detail is that mirroring the site with wget didn't work very well on the Internet Archive site (maybe wget doesn't support the BASE tag) so I had to do it a bit more manually—using _why's own Hpricot library to parse all the LINK, A and IMG tags.
The original soundtrack is also available in the download section on GitHub.