PortableApps.com is a platform for running your applications in a consistent manner on a USB flash drive. It has a nice customizable menu system. There are many applications that can run on the platform.
Main Site
https://portableapps.com/
Limited Number of Only Freeware/Open Source Applications
Commercial/Shareware/Freeware/Open Source Portable Applications, including .NET Applications
http://www.moreportableapps.com