"Portable Python" is a distribution of the Python programming language that

• can be run without installing it.
• from a USB drive, for example.
• includes many extras such as different IDEs, wxPython, etc.
• the exact set of extras available depends on the version of Python.
• can be obtained for Python 2.5, 2.6, or Python 3.0.
• is only available for Windows.

According to their official website, this distribution is not being developed anymore. However, the website is still worth a visit as they list several alternatives such as Anaconda that largely fulfill the same purpose.

If it interests you, another analogous distribution is MovablePython.