ALEKS has a full range of individualized online math courses for grades 3-12. They include ongoing assessment and course adaptation to the needs of the student.
In addition to its homeschool math courses with a teacher, MathHelp.com offers unlimited free practice for homeschoolers on all topics in Pre-Algebra, Algebra 1, Geometry, and Algebra 2. Select "view courses" to see all the options.
Khan Academy offers free online math lessons. Students can work on individual topics, but material is organized by grade levels as well as by upper level courses, and the system helps direct students to appropriate starting points.
MIT OpenCourseWare includes free prep resources for the AP exam for Calculus.
Multiplication Mini is a free app for desktops and mobile devices for practicing multiplication facts. Speed is adjustable and there are lots of interesting backgrounds from which to choose.
Learning Things has free placement tests for Saxon Math for all levels.
Dr. deLaubenfels offers free math resources on the Teacher Scholar Institute site, including textbooks and topical lessons for high school and college students.
WatchKnowLearn catalogs hundreds of free educational videos "Wiki-style" in both broad and sub-categories so it's easy to search. There are sub-categories for topics for all levels of math.
