Google’s experimental AOSP project was announced last month, which promises to bring the latest open source Android to the Sony Xperia S. Sony seems to be following through on their part by releasing their closed-source binaries, which are required for this project to be viable. These binary files are essentially closed boxes of proprietary code (custom drivers, graphics firmware, etc.) which drive the Sony hardware specifically. Without these files, it would be nearly impossible to get an AOSP build working properly.
Sony has also stated their commitment to the innovation that open source brings, and says that these binaries should allow an AOSP build of Android to boot to the home screen. Of course, these files won’t be useful to the casual custom ROM fan until developers manage to make stable builds from them, but this is the first important step to getting a full-fledged AOSP build of Android running on the Xperia S.
Hit the source for the downloads.