If you do a google search for Arduino Projects, you will find about 20 million links. Of course, not all of them are useful or even have correct information.
Of the many sites out there, I generally go back to six of them for great project ideas. If I am looking for project ideas, here are the ones I go to.
www.Sparkfun.com This site has great tutorials, great project ideas and you can buy most of the parts referenced in projects from this site. Since they contribute so much free content to the maker community, it is a store worth supporting.
https://www.adafruit.com Is similar to Sparkfun. They have a wealth of great project ideas, tutorials and stuff to buy.
http://www.instructables.com/howto/arduino/ This site is part of the AutoDesk company, which owns Eagle PCB software and autoCAD. It has thousands of Arduino projects to select from, as well as other make projects
https://makezine.com/category/technology/arduino/ This is the site from Make Magazine. It has thousands of projects for Arduinos, and for other sorts of projects.
https://create.arduino.cc/projecthub This site is part of the Arduino.cc organization.
https://maker.pro/arduino/projects This site has a lot of potential.
