Chemistry can be a challenging subject for many, especially high school. There are numerous resources online and offline that students can use to improve their chemistry skills and succeed. I have collected a list of few websites that have helpful resources for both high school and college students.

1) About.com's chemistry site is a very good place to start and they have few places for AP chemistry classes. Here is their link

http://chemistry.about.com/od/homeworkhelp/Chemistry_Homework_Help.htm

2)High school Ace's chemistry page has some resources too. This site is basically a collection of links and links to chemistry pages of various universities and websites. Here is the links for their weebsite.

http://highschoolace.com/ace/chemistry.cfm

3) Analyticalchem.info provides information mainly on analytical chemistry. This is helpful if you are trying to understand how different chemistry instruments work or are trying to do analytical calculations like concentrations, molarity, etc.Their link is:

http://www.analyticalchem.info

4)Royal society of chemistry has an amazing chemistry resource page for all. They have specialized sections for school students, teachers, college students, and even post graduates.

Their link is: http://www.rsc.org

The link to the school education page is: http://www.rsc.org/education/teachers/learnnet/

I classify this site as the best chemistry learning resource on the internet by far.

5)If you need help from someone on a specific topic, you can use the numerous chemistry forums on the internet.

The best forum with the highest activity is: http://www.chemicalforums.com/

They have a section dedicated to high school students.