Nowadays, on www.liveatc.net, there is an online communication of most air frequencies from around the world, but if you are interested in aviation, it may be more interesting to listen to such communications right at the airport or in places where there is no Internet connection. You will need an air frequency scanner.
All information about the purchase of the scanner is well described in the text by Mr. Pavel Svoboda on Aeroweb.cz - read here (czech language only).
And the best sites about radio communication in general are at kmitocty.cz (czech language only).
NDB