BonkEnc Portable is the popular BonkEnc packaged as a portable app, so you extract, convert, and encode your audio files just about anywhere you go.
You can place it on your USB flash drive, iPod, portable hard drive or a CD and use it on any computer, without leaving any personal information behind. It is packaged in PortableApps.com Format so it can easily integrate with the PortableApps.com Suite.
Open source and completely free for Windows.