Mixxx - Open Source Cross Platform DJ Software
I don't know if know if you the reader have ever been interested in mixing your own music, but if you have there are lots of tools out there that can get the job done. I have never really tried to mix my own music but I think software like Mixxx is a good place to start. It's open source with is good for development and it's cross platform which means no matter if you are on a Mac, Windows, or a Linux machine you can run this software.
Mixxx has everything you need to create a DJ Mix without the expensive equipment. If you are a beginner like me and don't have a Midi controller or a turntable Mixxx has features to duplicate that hardware. If you are more of a professional and have that kind of hardware Mixxx has you covered providing support for most midi controllers and vinyl control devices. You can use your built in sounds card as long as it has a line input which most do now a days.
Mixxx prvides all the tools you need to make a professional mix with BPM estimation, Parallel waveform display, Pitch-independent time stretch, Vinyl emulation, and Wave Recording. You can use several different audio types to you don't have to worry about converting audio to a specific format. You can save your mixes on the fly so you never have to worry about loosing your mix.
Mixxx is a free application for Windows, Mac, and Linux give it a try!