Mixxx is an open source DJ tool that can be useful for amateurs and professionals. This multi-platform program is loaded with features such as:

• beat estimation for you to know which songs that have a better sync match;
• adjust tempo without distorting music’s pitch;
• visual wave forms display;
• support for many different gears such as DJ consoles and MIDI devices;
• adjust the song’s low, mid, and high ranges;
• and more!

The UI seems simple enough to start using as soon as you install it.

The project seems to be under constant development from its team, which is good to know since the program has more chances of getting better and better.

Watch a pretty good tour video of Mixxx:

Have fun mixing!