Program: Fritzing
License: "GNU GPL v3 on the code and CreativeCommons:BY-SA on the rest"
Description: "Fritzing is an open-source hardware initiative to support designers, artists, researchers and hobbyists to work creatively with interactive electronics. We are creating a software tool, a community website and services in the spirit of Processing and Arduino, fostering an ecosystem that allows users to document their prototypes, share them with others, teach electronics in a classroom, and layout and manufacture professional pcbs."
Website: www.fritzing.org
Other: This application appears to already be portable, as it is downloaded without any installer. It may only be necessary to package this in portable apps format.