Python is an interpreter that can run "scripts" (.py
files). Therefore portablepython makes sense - if you don't want to install Python everywhere, but still want to run the small Python files. This helps if the target PC doesn't have Python installed (or you can't even do it because of privileges).
For C/C++ this doesn't make much sense as these are compiled languages. Just compile them to executables and you have your "portability".
If you need to "program C/C++ anywhere", just place your favorite compiler and code editor on a USB stick, and you're done. portableapps is a nice place to find portable (as in "USB carry-able" applications), and it has this link for a portable C++ IDE/Compiler.
P.S. Python programs can also be bundled into (rather large) executables using tools like py2exe and PyInstaller.