Tic-Tac-Toe is a simple way to give students alternative ways of exploring and expressing key ideas and using key skills. Typically, the Tic-Tac-Toe board has 9 cells in it, like that of the game. This can, of course, be adjusted.

Adaptations

Allow students to complete any 3 tasks--even if the completed tasks don't make a Tic-Tac-Toe.
Assign student tasks based on readiness.
Create different Tic-Tac-Toe boards based on readiness.
Create Tic-Tac-Toe boards based on learning styles or learning preferences.
Create Tic-Tac-Toe boards based on Multiple Intelligences.

From Fulfilling the Promise of the Differentiated Classroom by Carol-Ann Tomlinson

Additional Resources

Tic Tac Toe Template