Testing your Web Server Configuration
This is a running list of websites that will, well, test your website for different reasons, mostly security.
securityheaders.io an analyzer and rating system for your HTTP response headers
CFSSL “CFSSL is CloudFlare’s PKI/TLS swiss army knife. It is both a command line tool and an HTTP API server for signing, verifying, and bundling TLS certificates.”
Qualys SSL Labs This is the big behemoth of testing sites. They tend to be considered the defacto-standard for security testing.