PhET-The PhET website is your online lab for everything physics and chemistry. They have a huge bank of simulations for physics and chemistry, but also math, biology, and earth science. Some of the simulations are more like GAMES as well. Try energy skate park or lunar lander. There are also some pretty advanced simulations like bending light and quantum wave interference.
*Teachers: most labs even include a lesson plan with student worksheets!
CrashCourse-CrashCourse (youtube) has some of the best science lesson videos out there for chemistry and biology. There are even lessons for history, literature, and ecology, but the science videos are VERY well done. The material is pretty advanced so it's great for RHP chemistry and RHP AP biology. The host, Hank, is both interesting and dorky so it's pretty easy to keep up with him. If you have a hard time understanding material or want to review topics before a test, the CrashCourse channel is an excellent way to get it done!
SpanglerScienceTV (youtube)-Steve Spangler does a ton of science experiments on this youtube channel that are interesting, fun, and educational. I used this website a lot with chemistry students to get ideas for open house. Most importantly, I used a variety of videos so that students can SEE the different science reactions/laws/concepts that they've learned.
*Teachers: use TubeChop to cut the video and use the experiment to bring up discussion before a lesson, so that way Spangler doesn't simply explain the entire science behind the experiment but encourage students to figure it out on their own.