From http://www.spi.dod.mil/lipose.htm :
Lightweight Portable Security (LPS) creates a secure end node from trusted media on almost any Intel-based computer (PC or Mac). LPS boots a thin Linux operating system from a CD or USB flash stick without mounting a local hard drive. Administrator privileges are not required; nothing is installed.
LPS-Public allows general web browsing and connecting to remote networks. It includes a smart card-enabled Firefox browser supporting CAC and PIV cards, a PDF and text viewer, Java, and Encryption Wizard - Public. LPS-Public turns an untrusted system (such as a home computer) into a trusted network client. No trace of work activity (or malware) can be written to the local computer. Simply plug in your USB smart card reader to access CAC- and PIV-restricted US government websites.