For the kids who progress through the standard math ladder so quickly that they need some side paths.
Work and Puzzle Books
Books
Light-hearted: Murderous Math Books Serious: Logic Puzzle books by Martin Gardner History/Fact books by Ian Stewart Oxford Mathematics Study Dictionary by Frank Tapson
Interesting College Textbooks
Crossing the River With Dogs A Human Endeavor
Online Math Discovery
fractal drawing software Mathcounts Minis Alcumus
Documentaries
Online Courses
Teaching Company Courses - Joy of Mathematics Thinkwell courses with Dr. Burger Side Paths Ciphers and Codes Centre for Innovative Mathimatics Teaching Public Key Cryptography The CryptoClub (workbook available for free here) Highly Regarded Math Textbook authors: Richard Rusczyk, Harold R Jacobs,Tom Apostol
SOTW and Other Resources 