Radio Site - How To Create It?

Hello guys, my cousin wants to have his online radio site (with music etc) and I wonder does anyone of you guys know any good plugin that is easy to use for WordPress (or just to connect with WP) so you can create your own playlist etc...

Depends on the functionality you are looking for. Are you wanting to stream an online radio station? Or do you want to create a predefined list of songs?
Check these out (I don't own or gain any money from this recommendation).
Audio Dock, Hero, Royal Audio Player, tPlayer, SoundCloud, PowerPress Podcasting, Zoom Sounds.