This site not only has excellent videos explaining concepts you learn in math, but also all of your other subjects.  Check out the section called "practice, knowledge map" as well as the brain teasers.
Patrick JMT = Patrick Just Math Videos.  Patrick's clear and concise style is an excellent way to clear up areas where you need a little extra explanation.
Discovery Education
This is an incredibly rich site, with many links to websites offering help in all areas, not just math.  Don't worry about the login, the free sections are terrific and are screened by the site.