McDougal Littell (additional practice related to the book)

Khan Academy (add @mrhartzer as your teacher if you wish)

Desmos Calculator (online graphing calculator)

GeoGebra (online/downloadable geometry software)

Wolfram|Alpha (comprehensive online mathematics problem solver)

Wolfram MathWorld (comprehensive online mathematics encyclopedia)

Math Games (practice basic K-8 skills)

YouCubed (additional videos about learning mathematics)