Netbook OS

Jolicloud

    http://www.jolicloud.com/

Moblin

    http://moblin.org/

Meego

    http://meego.com/

Ubuntu Netbook Remix

    http://www.ubuntu.com/netbook

Chrome OS

    http://www.chromium.org/chromium-os

Android OS

    http://code.google.com/p/live-android/downloads/list