Distributions:

http://www.archlinux.org/

I use these , because its a simple and lightweight Linux Distribution. I don´t really need a Linux-Distribution only for Musicmaking , so i use Arch. I think its one of the best linux Distributions!

http://64studio.com/

is a free operating system based on Debian designed for creative users on x86-64 and legacy 32-bit hardware architectures. It intends to serve as an all-in-one solution for audio and video recording, editing, and other forms of media production.
Since 64 Studio is distributed with a free software license, anyone with a 64-bit computer can install it on their computer (in place of or alongside the well-known Windows operating system). An alternative installer is available for systems with 32-bit processors.

http://ubuntustudio.org/

Ubuntu Studio is aimed at the GNU/Linux audio, video and graphic enthusiast as well as professional. We provide a suite of the best open-source applications available for multimedia creation. Completely free to use, modify and redistribute. Your only limitation is your imagination.

http://www.dynebolic.org/

 dyne:bolic is shaped on the needs of media activists, artists and creatives as a practical tool for multimedia production: you can manipulate and broadcast both sound and video with tools to record, edit, encode and stream, having automatically recognized most device and peripherals: audio, video, TV, network cards, firewire, usb and more; all using only free software!

MUSIX

http://musix.org.ar/

GNU+Linux is a Live CD and Live DVD operating system for the x86 processor family based on Knoppix, Kanotix and Debian. It contains a collection of software for audio production, graphic design, video editing and general purpose applications. The initiator and co-director of the project is Marcos Germán Guglielmetti.