A teacher-run site that provides a Collection of Math Crosswords (5-11 Grade) with answers provided directly below the puzzles for quick verification.

For those looking for interactive options, the Online Test Pad offers digital math crosswords that provide instant feedback on whether your answers are correct.

Another variation on Infourok covers complex numbers and higher-level functions.

Математический кроссворд для 10-11 классов - Инфоурок

This site features detailed methodological developments that function like blog posts.