MultiBoot USB
This is a project that contains a collection of GRUB files and scripts that will allow you to create a pendrive capable of booting different ISO files.
Porteus is a fast, portable and modular live CD/USB medium based on Slackware Linux. The distribution started as a community remix of Slax, another Slackware-based live CD, with KDE 3 as the default desktop for the i486 edition and a stripped-down KDE 4 as the desktop environment for the x86_64 flavour. The lightweight LXDE is available as an alternative desktop environment.