Do you know PeaZip?

[zAchAry]

Flexibility
PeaZip can extract most of archive formats both from Windows and Unix worlds, ranging from mainstream formats as 7Z, RAR, TAR and ZIP to experimental ones like PAQ/LPAQ family, currently the most powerful compressor available.
PeaZip supports creating archives with a wide range of compression and encryption standards, and allows to export job definition as scripts to bridge the gap between GUI and console applications, and let the user pick the best of the two worlds.
PeaZip is a reliable solution for most of the archive types you may met, and will help you in finding the right tool for a wide range of specific needs if you are searching for speed, or maximum compression, or strong encryption.

Portability
You can use PeaZip on all Windows version and on Linux (PeaZip is a desktop neutral application) with the same features and look and feel; moreover, for both platforms, PeaZip is also available as standalone, portable application not needing installation.
You can bring PeaZip with you and rely on it on multiple platforms.

website: peazip.sf.net
search for: standalone for Linux

what do you think? (an actual portable software with no need to install at all)
note: I liked it more on Win32

[pwatk]

Without trying to sound like a cretin (I can do this quite well sometimes ), I'm pretty sure you could just compile p7zip as a static if you need it to be portable. It would give you the same functionality!