What is a portable application?
Overview of sources for portable applications:
http://www.pendriveapps.com/
http://www.portablefreeware.com/
http://portableapps.com/
http://www.liberkey.com/en.html
http://www.snapfiles.com/features/portable-apps.html
http://www.lupopensuite.com/suite.htm
Its possible to combine portable applications from different sources and use a different launcher for them: