Plasma/InstallingNext
How to install test versions of Plasma Next
Kubuntu
http://blogs.kde.org/2013/07/31/project-neon-5-daily-builds-ubiquity-wireless-setup
openSUSE
openSUSE offers snapshots from git master updated frequently as well. Add the KDE:Unstable:Frameworks repository (http://en.opensuse.org/SDB:KDE_repositories#Plasma_Next) and the Qt53 repository (available at the same link) and install the plasma-next-session package to have a session available at the next login.
Gentoo
`layman -a kde && layman -a qt`, `emerge @kde-live-next` and a daily run of 'smart-live-rebuild' which will only update packages that really got new commits.
From Source
Following the instructions here it will automatically build all KDE software that has a KF5 port, most notably the Plasma workspaces, but also development previews of Kate, Konsole and Dolphin.
Afterwards follow the guides for "Runtime setup" and then run "kwin5 --replace" and "plasmashell".