There are two versions of APSIM available.
APSIM Classic (last release version was 7.10)
Please note there will be no more major APSIM Classic Releases. However, there are currently more models available in APSIM Classic, so please refer to this list – Models in Release – APSIM
APSIM Next Generation.
A new generation of APSIM was released in October 2014 following construction of a proof of concept. Since this early version, new models have been added and the infrastructure has been refined. The development team have improved the functionality, increased run time and provides auto-generated documentation. All new development with APSIM is made in this version. The list of models in Next Generation can be found here – APSIM Next Generation
There are a number of other products that can also be accessed at the registration page, including APSoil.