SARDU

http://www.pendrivelinux.com/sardu-multiboot-usb-creator-windows/ 
WARNING! I've been informed that SARDU is now potentially packaged with the malicious Adware "Win32/Somoto.A". As a result, I highly recommend you avoid using this tool. Back in Jan 2011, when this post was originally written, SARDU was a good clean tool! 
www.sarducd.it/