Bitcoin Core version 0.15.0 is now available from:

https://bitcoin.org/bin/bitcoin-core-0.15.0/

and

https://bitcoincore.org/bin/bitcoin-core-0.15.0/

For the release notes please see the git repository:

https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.15.0.md

Preferably use the above download link, not the below links to download the source tarball, as the release tarballs are generated deterministically and GitHubs's are not.