A pair of articles on advanced template mechanics -- Eli Bendersky and Eric Niebler
If you're a very advanced C++ developer with an appetite for template mechanics, these two articles that were posted in the past 24 hours may interest you.
Note: The vast majority of C++ developers don't need to know this, but very advanced developers will find the material and the techniques interesting.
SFINAE and enable_if
by Eli Bendersky
Customization Point Design in C++11 and Beyond
by Eric Niebler