@joe_bower said he was looking for some decent math games online and couldn’t find any. I remembered that I used to make math games all the time so I fired off a bunch of links back. I decided it was worth gathering all those links into one spot. Who knows, maybe some of these old games are useful.
Good for teaching about perspective: Labyrinth
Gives students a feel for how fraction operations work: Fractions operations
Practice operations and solve a number puzzle: Countdown
Practice factoring numbers & remember prime numbers: Factors!
Just a fun spaceship game (similar to Asteroids): Spaceship game
Useful for recognizing some similar fractions: Horse Races
Really just algebra practice & puzzle solving: Algebra puzzle
More of the same type as practice as above but quadratic algebra: Quadratic algebra puzzle
Look at patterns when moving rings: Towers of Hanoi
Try a variation of the classic logo programming language: Logo Programming