have i been pwned? - Check if your account has been compromised in a data breach
DeHashed - DeHashed is the largest & fastest data breach search engine.
LeakCheck - Data breach search engine, low price starting from $10/mo, one email address for free, unlimited API, 7B+ entries
Profil3r - The Dead Frontier Profiler : Full of useful information for boss hunting, looting, and enjoying Dead Frontier, the zombie MMO.
Snusbase - The industry leading database lookup.
Firefox Monitor - Firefox Monitor arms you with tools to keep your personal information safe.