Here is the stable 0.9.21 release and the mtn builds based on it
Release notes are published under the official www.i2p-projekt.i2p.xyz page.
Remember: from the release 0.9.18 on you need Java 1.6 to run I2P, SUNs Java 1.7 or 1.8 IS REALLY preferred!
No more headless installer files - thanks to a update of the installer package the i2pinstall.exe can be run headless!
If you have installed I2P from the PPA, have a look on I2P debian installer page and look for updates in the PPA.
Use: java -jar i2pinstall-0.9.21.jar -console.
i2psource-0.9.21.tar.bz2.sig .sig file for the source
i2pupdate-0.9.21.zip update package