Here are some useful links for you and your student:
Funbrain.com
This is a good site for K-8 students. It has games and activities to help enrich your child in all subjects.

Brain Pop
This site has animated videos for topics in all subjects and fun educational games. The only drawback to this resource is some of the content on the site is free and some has to be paid for.

How Stuff Works
Sponsored by the Discovery Channel, this website has videos and articles explaining to students how things work in many different categories. It also contains quizzes connected to the different topics it explains.

Kids Know It
A free resource for all subjects. It includes videos, games, and other great resources for all students.

Wolfram: Computational Knowledge Engine
This is a great resource for looking up different conversions and other facts. A good place to double check work or brush up on facts.

Crash Course (by the Vlog Brothers)
Quick 10 minute videos giving very detailed summation of topics in world history, US history, chemistry, literature, biology, and ecology. I highly recommend this channel for quick reviews and just to introduce yourself to a new topic.

C.P Grey
Short videos on a variety of interesting educational topics. Highly recommend for his fun, fast delivery.

TED Ed
Videos from the same people who bring TED Talks, your chance to talk 10 minutes about something that inspires you. The videos are fun, cover a variety of topics, and are always interesting.