Depending on the grade/level...

ALEKS is great for assessments, practice and reporting.

Mathletics also provides reporting and practice, but a little more "fun" and game-based.

IXL Math is good, but doesn't provide instruction.

I also like Gizmos, Aha! Math and Adaptive Curriculum for instruction and practice.

Maybe a combination of ALEKS (for reporting/assessment) and Mathletics/Adaptive Curriculum/Aha! Math for fun, interactive lessons.

Daa'iyah Na'im
Director/Head of School
The AGVI Academy for Gifted Youth
http://AGVIgifted.org