Fritzing and circuits.io are two awsome tools for electronics engineers and hobbyists.
Fritzing is a desktop application which helps you to draw your circuit with real image of components. Also can design schematics and pcb layout. You can save your code also in the same fritzing file. I am using fritzing to make images of circuits that can be imported as jpg or png and can share in my blogs even in arduino create web IDE.
I am not big fan of fritzing schematic/ fritzing pcb layout.because the auto rooting ability is not very good in fritzing.But you can find all DIY electronics parts in fritzing.And there is no need of internet connection for fritzing.
Circuits.io is also very cool tool. It is Web based.you can make circuits using real images of components like in fritzing.The main attraction that i felt to circuits.io is you can simulate your circuits using this.also there is pcb layout and schematic functionalities.BoM tool in circuits .io is very cool.
As a professional I prefer eagle for pcb design.I never uses fritzing/circuits.io for pcb design. but as a hobbyist and blogger I love these two tools.You can directly share the projects in circuits .io to facebook,reddit,etc and also embedding html is also available.For show and tell tutorials it is nice to show some pictures in fritzing or simulation in circuits.io than simple schematics