Arcademic Skill Builders – Variety of fun math games on every topic - Language Arts and Geography games available, too. Grades 1 – 5
Coolmath4kids.com - Covers a wide variety of math, good for class activity or reinforcement on their own.
Scholastic’s Study Jam – Videos, music and jams on Math and Science. Great instructional resource, as well as independent instruction and practice. - studyjams/index.htm
IXL.com – "comprehensive math practice site" - (Requires subscription?)
Math Master – Videos and worksheets -
BBC Bitesize Kids – English, Math, Science (app available too)
APlus Math - Play games, practice flashcards, create your own flashcards, print off practice worksheets to improve your skills, or get homework help from this website.