Some links I like.
The Program of Mathematics Education
MacTutor History of Mathematics Site -- St. Andrew's University
Math Forum (alias Geometry Forum)
Furman University Mathematical Quotation Server
Desmos (FREE! Graphing Calculator)
GeoGebra (FREE! Interactive geometry, algebra, statistics, and calculus software)
EMAT 6690 Essays
EMAT 6690 Instruction Materials
8th grade Instructional Unit: Exponents, Square Roots, Pythagorean Theorem - click here
Cool iPhone apps for teachers and students:
(As seen in the Scholastic Instructor, Spring 2013)