Several sites offer free answers for students with tough math questions. At Ask Dr. Math, students can search the archives to see if their question has been answered, or write to Dr. Math. Another option is Studypool.com, which offers answers for other subjects as well.
If you are looking for more in-depth help, other sites post lessons for every grade level from elementary through high school. Freemathhelp.com offers lessons, games and forums in algebra, calculus, geometry, and trigonometry, among others. In the forums, users write about everything from basic arithmetic to advanced differential equations. Another option is to check out the many online tutor sites, such as Tutor.com.