Texas Education Agency - Released TAKS Tests
Mathwizz - This site has interactive problem generators. Students can get practice making and solving problems in the following categories: arithmetic, fractions, integers, decimals, algebra, geometry, statistics, conversion math.
CuriousMath.com - Want to learn how to quickly square a number that ends in 5? Or how to tell if a number is divisible by 3? Or maybe you'd like to know why the number 153 in the Bible is such an interesting number? That's the kind of fun and fascinating math tricks and trivia you'll find here.
Math Tools - from the Math Forum. Some very cool tools. You have to register, but there's no charge.
National Library of Virtual Manipulatives - from Utah State University - exactly what it says it is. Some of the coolest stuff since spaghetti was invented.
Mathwords - a dictionary/encyclopedia for math and math-related terms
NEIRTEC - Links to some very nice virtual tools, organized by Algebra Readiness Indicators.
MacTutor History of Mathematics archive - from the University of St. Andrews in Scotland. Great history of math reference. Also, click on "Famous Curves Index" to get some pretty nice java applets that let you manipulate parameters and see the outcome in the curve.
Algebrahelp.com - a collection of tools created to assist students and teachers of algebra. Check out the calculators.