PNGOUT – this is a FREE tool that reduces the size of PNG files by 5 – 30%. Running this on all images for presentations, blog posts and web sites is a pretty good idea!
Google - good old Google can be used to query sites looking for login information
Wayback Machine - can be used to look at previous versions of your site to see what files are changing, and can be used nefariously to try exploit old code
Shodan - can be used to search and reveal sensitive certificate information about your domain
Web Check - can be used to pull security information about your sites
DNS Dumpster - can be used to get a list of host records for a particular domain
Dehashed - public breaches, search e.g. domain:iua.co.za
’;–have i been pwned? - free tool for monitoring your email addresses appearing in data breaches