Fun Brain has math and literacy activities 

www.funbrain.com

Nick Jr
http://www.nickjr.com

Starfall  has phonics and reading games
http://www.starfall.com

PBS
http://www.pbs.com

Get Ready to Read has literacy games for young children
http://www.getreadytoread.org

Pebble Go has interesting information and games about animals, earth & space, social studies topics, and biographies. Contact your teacher for the username and password.
http://www.pebblego.com/login.php 

More Starfall has math and literacy games by grade level. Contact your teacher for the username and password.

http://more.starfall.com/m/welcome/index/load.htm

Xtra Math provides math practice for children after you set up a free account.

http://xtramath.org/