Enter BlackArch Linux, a package repository for arming your Arch Linux box to the teeth with all our favorite tools. There's also a collection of Live images to play with if that's more your style, but this relatively young project offers an appealing choice to those who prefer Arch. Getting BlackArch up and running is pretty straightforward.
I prefer to start with a basic Arch Linux installation. For the command-line adept and those familiar with Arch, the Arch Installation Guide is a no-nonsense checklist of things you need to do, while the Beginners' Guide offers a bit more hand-holding. I used both when getting back into Arch Linux a while ago. You'll need to partition your drive, format the filesystems, pacstrap it, set up the network, add a user, and some other basic things that are outlined in the guides. Installation difficulty is on par with OpenBSD, but with a little less guidance from a dedicated install script. Don't forget to set up a boot loader!

Once you have Arch installed and a comfortable userland configured, you'll want to make sure it's up to date by running "pacman -Syu" and then you should install wget before moving on to installing BlackArch, if you haven't already:
pacman -S wget
From there, you can simply follow the instructions on the BlackArch Download page. This will just add the repositories to your Arch Linux installation, and doesn't actually install the packages. You can opt to install all the packages at once with:
pacman -S blackarch
But in my opinion, the fact that you can pick and choose which tools to install makes it quite nice for devices like netbooks or other machines that you really don't want bogged down with hundreds of tools you don't need. The BlackArch download page outlines how to peruse their repository for the stuff you want, or installing groups of similar packages, such as "blackarch-scanner" and "blackarch-networking"
In my next post, I'll explain how to configure OpenVAS, and get it up and running on BlackArch. I frequently set this up in my security lab when introducing interns to vulnerability scanning, and it's usually a bit tricky to get running for the first time.