Here you will find the packages with the current simpleSAMLphp versions:
SHA256 checksum: ab1a71a4eed2c086774829d47ce72137e4d1a7bd6b8a2535b4a1ddfd6e7da51f
Check the GitHub releases page in case you are looking for any other version.
The core library handling the basic SAML stuff (messages, bindings, and so on) has been detached from SimpleSAMLphp, and can now be found in github:
SimpleSAMLphp itself has been moved to github too, and you will find it here:
Make sure you follow the instructions to install from the repository.
SimpleSAMLphp is available as a Debian package. You can therefore install it with apt-get, but bear in mind that the version available in Debian stable might be outdated. Since Debian backports security fixes, it is fine to use the version you may get with apt-get, but you will miss the latest features.