Sheppard Software (All Ages)
Funbrain (K-8)
Discovery Games (Grade 3 and Up)
Fun School (Prek-grade 6)
National Geographic Channel's Games Site (Grade 3 and Up)
Educational Games on Nobel (Grade 6 and Up + Higher Ed)
Prongo (Prek- middle school)
Childtopia (Prek- Grade 6)
Game Classroom- Excellent, safe, teacher-approved, state-standard aligned games for grades K-6
Gameaquarium- Great site for games for kids K-6 in all types of subjects
Braineos- nice site where games are based of flash cards
Tucoola- site full of skill-building games for younger kids (parents can track progress)
Tutpup- math and spelling games
BrainNook- math and English games
CleverIsland- fun educational games for kids 3-8 in various subjects
What2Learn- educational games where a teacher can track students progress