draw.io – create diagrams, wireframe and flowcharts in the browser.
faxzero.com – send an online fax for free – see more fax services.
builtwith.com — find the web hosting company, email provider and everything else about a website.
remotedesktop.google.com — access other computers or allow others to remote access your computer over the Internet.
homestyler.com – design from scratch or re-model your home in 3D.
random.org – pick random numbers, flip coins, and more.