Live ATC

https://www.liveatc.net/

Here you can listen communication between real world pilots and air traffic controllers. Many airports from all over the world are listed, including Václav Havel airport – LKPR.

Flight Radar 24

https://www.flightradar24.com/

Great page for aviation enthusiast. You can watch real air traffic almost in real time. You can view flight path, altitude, airspeed, origin and destination and even photo (if someone ever took a picture of that particular aircraft) for every displayed airplane.

Windy

https://www.windy.com/

This website offers awesome wind prediction in the form of simple animation. You can see what the wind is to be like on the whole planet and at various altitudes. And not just the wind, you can view temperature, pressure, humidity, clouds, precipitation and also waves.

Skyvector

https://skyvector.com/

This site contains VFR and IFR aviation maps. In the beginning, only the USA and Alaska were covered, but the coverage grown worldwide. Very good source of charts, which is also free.