SANS
MAXMIND GeoIP
MAXMIND maintains an incredibly accurate geoip database.
https://maxmind.com/en/locate-my-ip-address
https://maxmind.com/en/geoip-demo
Hardenize
Comprehensive domain configuration test built by Ivan Ristić.
Qualys SSL Labs
SSL/TLS testing for:
Server: https://www.ssllabs.com/ssltest/
Browser: https://www.ssllabs.com/ssltest/viewMyClient.html
Email Message Header Analyzer
Format email message headers into an easily readable format.
Security Headers
Analyse all HTTP response headers from a website against current and emerging security best practices.
Content Security Policy (CSP) Evaluator
Test Content Security Policy (HTTP Response Header) configuration.
https://csp-evaluator.withgoogle.com
Crypto
Code-Breaking, Cipher and Logic Puzzles solving tools.
https://www.boxentriq.com/code-breaking
Web app offering modular conversion, encoding and encryption online. Translations are done in the browser without any server interaction.