This is a NASA site which provides a graphing tool for middle and high school students to graph equations, physics simulations, or plot data fields. The site provides lessons, curriculum, standards, and resources to connect the use of MathTrax into the classroom.
This site has online manipulative activities. Grade levels are separated by Pre-K-2, 3-5, 6-8, and 9-12 and topics number and operations, algebra, geometry, measurement, and data analysis and probability.
This site provides over 100 free online activities to match mathematics with the real world. The site provides detailed lesson plans and connect the activities with the NCTM standards.
Algebra topics are separated by preliminary, beginning, intermediate, and advanced levels. Each individual topic's lesson includes definitions and examples. In addition, practice problems are provided with answers and hints.