What is a good software I could download for free that would allow me to make mashup songs?

I'm interested in starting to create my own mashups and start DJing. I don't want to buy turntables or expensive software just yet because I'm not that experienced and would not want to waste money; plus this is just for my own pure enjoyment. If someone could give me a link to a website that allows me to download some sort of software that is free and NOT a limited time trial that would be grand. Thanks.|||http://www.hongkiat.com/blog/25-free-digital-audio-editors/