It is also available as a zip file for those who are unable to install software on their system. This is not well tested and needs to be placed in the root of a drive. You will need at least 3.5GB of free disk space.
You are advised to also download the accompanying md5, and check the integrity of your download.
If you have already downloaded and installed PortableGIS 5.8 then there is a patch for qgis, available as a zip file (qgis2.zip), that can replace the existing folder. This will overwrite the entire qgis folder so take a backup if this is a problem
The source files for generating Portable GIS from the basic software are now available at https://gitlab.com/archaeogeek/portable-gis. This is a work in progress- pull requests and issues gratefully accepted. See the developer documentation at Read The Docs for instructions.
Previous versions of Portable GIS can be downloaded from the archive but you are advised to use the latest version where possible.
A note on speed
Portable GIS requires a USB stick with a fast read/write speed. Your average free USB stick from a a conference will not work. Please see these benchmark tests or consider purchasing a USB stick using this Amazon Affiliates Link.