Last month it was revealed that Google's Jean-Baptiste Queru was kicking off an "experiment" to bring Android Open Source Project support to the Sony Xperia S, with the aim being to try and bring a vanilla AOSP version of Android to the device. Sony voiced its support for the project days after it was announced, and now the company has made the binaries (things like hardware drivers and other necessities) for the device available for download. Additionally, Sony says that one of its software engineers will be able to help the project along and contribute patches when necessary.
As Sony notes, there's still "a lot" of work on this project to be done, but these binaries should be able to get an Xperia S booted up to the home screen. That's obviously kind of an important step, and I'm sure that the developers involved in the project are glad to see Sony actively supporting it. It's still not clear when or if we'll see something that's suitable for normal use, but hey, progress is progress. You can find both the full announcement of today's release as well as the Xperia S binaries at the Sony link below.