MAXMIND maintains an incredibly accurate geoip database.
Comprehensive website configuration test built by Ivan Ristić.
Qualys SSL Labs
SSL/TLS testing for the browser or server.
Analyse all HTTP response headers from a website against current and emerging security best practices.
Email Message Header Analyzer
Format email message headers into an easily readable format.
Content Security Policy (CSP) Evaluator
Test Content Security Policy (HTTP Response Header) configuration.
Code-Breaking, Cipher and Logic Puzzles solving tools.