Mesa, the Open Source OpenGL implementation has released a new major version which includes support for OpenGL 3.1. The release announcement can be found here.
Although Mesa works on multiple platforms, including Windows, it's on open source operating systems like Linux where it is most important. On Linux, Mesa provides hardware accelerated OpenGL when running open-source graphics drivers. This means that if your graphics card is supported, you will get hardware-accelerated OpenGL 3.1 out-of-the-box on operating systems such as Ubuntu and Debian, even when running from a Live CD or bootable USB stick.