Redox is still at the experimental stage, but there's lots you can do with it, and it's fun to try it out. You can download and run the latest release. See the instructions for running in a virtual machine or running on real hardware.
Building Redox has information about setting up your system to compile Redox, which is necessary if you want to contribute to Redox development. Advanced Build gives a look under the hood of the build process to help you maintain your build environment.