The Joomla CMS has a couple of places from which you can download the latest CMS versions. Below is a list of locations where you can find Joomla.
Joomla Download Page
If you would like to download the files already built into an easy zip file format you can download them directly from joomla.org. On this page you’ll find the most recent release of the Current stable version and links to other Legacy versions.
This download page pulls the files from a list available on JoomlaCode site. If you wish to browse specific packages, including every release since 1.0, you can do so by visiting the Files directory on JoomlaCode.
Alternatively if you are interested in looking at the files before you download or would rather review and download direct you can do so from the Joomla GitHub repository. In the repository you can use the tags feature to select the version of the code you wish to download.
Note: Nightly builds
Nightly builds are available from https://developer.joomla.org/nightly-builds.html and can be used to test both new installs and updates from previous releases. These packages should not be used in production environments.