[2007-12-27] The Missing Manual: Mac OSX Leopard Edition
Unlike Mac OS X Leopard Pocket Guide, this is the book you really should buy if you are running Leopard.
[2007-12-11] Improve QuickLook in Leopard
Leopard's new "Quicklook" is a nice tool, but for stubborn old command line types like me, it has some limitations: it won't show me plain text files unless they have the extension ".txt".