haveibeenpwned.com Check if you have an account that has been compromised in a data breach.
monitor.firefox.com See if you’ve been part of an online data breach.
Data Breaches Privacy Rights Clearinghouse’s Chronology of Data Breaches.
IsMyEmailWorking.com A simple & Accurate Way To Test Your Email. Try the Advanced Email Test to see your email go through it’s steps.
IsNotSpam online spam checker was created to help you test email and newsletter content, and alert if it is likely to trigger spam filters.
Browser Finger Print Testing
deviceinfo.me will display all the information being revealed by your browser.
panopticlick.eff.org is run by Electronic Frontier Foundation.
amiunique.org is another good resource and is open source.
DNSleaktest.com DNS Leak Test Check to see if your DNS is being leaked to your local ISP.
ipleak.net IP Leak Test Check to see if your real IP is being leaked via your VPN.
Astrill IP Leak Test Check to see if your real IP is being leaked via your VPN.
Wigle Wireless Network Map Find your wireless network on a public map. Look at a close road and not directly at your home on the map.
Qualys SSL Labs test your sites SSL cert.
Qualys BrowserCheck Qualys BrowserCheck will perform a security analysis of your browsers and plugins, and will run several system checks.
ipqualityscore.com Quickly perform domain reputation checks to identify domains being used for abusive behavior. Examples include phishing, malware, hosting email addresses used for fake account creation and chargebacks, and similar types of malicious behavior.
Tools of the trade
All Things Mac