This website provides news articles about primarily biology topics but the topics are pretty advanced so this information is most pertinent to high school students.
This site links to chemistry classroom management and activity resources. It also has a lot of fun links that relate chemistry to other subject areas from history to poetry.
I hesitate to put this up here since this is technically about college students but I feel that there are a lot of similarities about what they say in the video that is relevant to the lives of college students is also highly relevant to the lives of high school students.
This site is maintained by a high school biology teacher. It includes notes / study guides, interactive quizzes, online activities, and numerous science links relating to all biology topics.
This site has various resources for elementary, middle and high school grades. Something especially interesting is the free video series titled "Women Are Scientists."