itDJ is a free easy to use DJing package for OS X. Although it's very simple, it features some useful features such as integration with iTunes library and playlists.
The layout of itDJ is straightforward. In the main window of itDJ there are two mixing decks. Around these two decks are the DJing tools i.e. display title, equalizer, speed indicator, crossfader and cue buttons for loops and beats. There are also several other special effects tools.
With these tools you can create some original mixes but if your imagination is limited, there's even an automatic mixing mode that will attempt to mix your iTunes collection for you based on the beats-per-minute of the tracks.
However, itDJ is a very limited package in general. There's no way to connect external devices for example and there's not much control over advanced aspects of your sound and mixes. itDJ is also in beta which means it can also be unstable.
itDJ is an ideal package for beginners although advanced DJs will find it lacking.