ABCYa - click on your grade level
BrainPop, Jr. - educational videos
Internet4Classrooms - tons of Language Arts and Math activities organized by grade level.
IXL Math - interactive
Riverdeep Math - NISD math program; click here for Parents' Guide. math site by grade level
Starfall - this fantastic site makes learning to read fun for PreK through second graders and English language learners
TumbleBooks - e-books for e-kids