A key benefit of Windows Home Server is the versatility and power it offers as a development platform. Even when Windows Home Server software was still in the beta stage, we published a software development kit (SDK) so that 3rd party developers could develop interesting add-ins for the product. See the original post, "Developers, Developers, Developers".
There are currently 100+ add-ins developed for Windows Home Server (up from 70+ in January of this year). We have a dedicated Windows Home Server Add-ins page on the Microsoft web site. There are also a number of other sites dedicated to this topic, such as the Forums on We Got Served and Windows Home Server Add-ins.
At the Professional Developers Conference last fall, we received a huge amount of interest in Windows Home Server from the developer community (standing room only in information sessions). MSDN availability will increase awareness of Windows Home Server with a larger community of professional developers and help further grow the ecosystem of software applications built for Windows Home Server. Effective today, Windows Home Server is available under Operating Systems on the MSDN Subscriptions Download Page. (Instructions for downloading.)