Here you will find some tips, tricks and links to utils. This list will grow as I regularly will add new stuff:
Domain / web related:
Nice online IPCalc: http://www.ipcalc.org/
Check your SSL Cert: https://www.ssllabs.com/ssltest/
Check you MX records: http://mxtoolbox.com/
Check e-mail blacklists: https://rblwatcher.com/ – with free monitor
Check e-mail blacklists: http://www.anti-abuse.org/multi-rbl-check/
Windows Command line:
Win7 missing Telnet? Download PuTTY or run:
Change password from command line (the * will prompt you for the new passwd):
net user USRNAME *|NEWPASS [/domain]
ipconfig output long as a terms of service document? Pipe to find (like grep in Linux)
* The word “Address” is OS language specific, so you might want to change it to your locale version.
ipconfig |find "Address"
Win: Reveal your stored browser passwords: http://www.nirsoft.net/utils/web_browser_password.html