Here are some links that you may find interesting, helpful, or amusing!
InterAct Math
NHS Google Site
eCalc Online Scientific Calculator
www.hippocampus.org
Mastermind online
Rubik's Cube online
Trigonometry applets
Daylength data
Online stopwatches
Make-a-flake
Utah State University's National Library for Virtual Manipulatives
for Interactive Mathematics
The Math Forum (at Drexel University)
The Park City Math Institute
SAT Question of the Day
High School Hub
Mathmistakes.info
TimeandDate.com
Mathplotter.com
Graph Paper
More Graph Paper
Math.com
Mathwords.com
A collection of Math Applets
Cool Math Graph It!
Mathagon