There is plent of stuff out there and they typically have a demo version that you can test drive the software out with.
I personally use FL Studio. They have three different versions you can buy depending on what you want to do with it. You can mix, remix, create, and format music through it. Plus it is a great DAW for all sorts of VST programs.
There is also, Ableton Live, Pro Tools, Reason, Logic, Qubase.
If you are looking for strictly DJ software try Traktor Pro 2, it is great DJ software for mixing/ recording/ goofin around.