Everything you want to know about security, from a Mac perspective. https://www.securemac.com/
A very well-organized site for Mac power users trying to get up to speed on Mac OS X. https://www.macosx.org/
A compendium of tips and tricks for serious OS X users. https://www.macosxhints.com
Comprehensive source of “real-world” advice from Ted Landau and crew. This is one of the Web’s best Mac resources and there’s no shortage of OS X info here. https://www.macfixit.com