Wordstat
Also: Yandex Wordstat
A free Yandex tool that shows query volume and related expansions.
Wordstat shows how many times a phrase was searched, which other queries contain it, and what the same people searched for. There is a query history, which reveals seasonality.
Quotes and the exclamation mark refine the volume: "phrase" is only that phrase, "!phrase" also keeps the word forms fixed.
Full explainer
Yandex Wordstat: a beginner's walkthrough →