WebMatrix is a compilation of technologies that MS has put out over the past few years. Off the top of my head, they include: Visual Studio Web Developer Express, SQL Server Express, IIS Express (which is IIS stand-alone, but bundled with WebMatrix, so don't hold your breath for a stand-alone distributable of IIS, which would be real awesome).
Recently, MS released the Web Platform Installer WPI, which is a master installer that checks for the existence of IIS, .NET 2,3.5&4, ASP.NET, ASP.NET MVC, SQL Server Express, then installs and configures those applications if they are not there. It actually works most of the time, and does a good job registering ASP.NET into IIS.
Additionally, the WPI will read a default RSS feed from MS, which publishes popular Open Source IIS applications, like CMS, Blog and ECommerce systems. WPI can be configured to read third-party RSS feeds. These applications are installed with default settings, or really the settings they had when a developer used MS's web deployment wizard, or web package builder to create them -- dig too deep into this technology, and you'll get woozy quick.
Having spent a month building an installer for an enterprise ASP.NET application, and watching it fail 50% of the time due to ACL restrictions, I can say that WPI and it's deployment packages are an ambitious task, and they've done pretty well.
Now, MS has an package manager for OSS projects called NuGet, which is like apt-get, I suppose. I've seen it begin to crop up on git hub. Hard core OSSers will find this all odd: a whole ecosystem being built and advocated by MS, around open source software which will, Mono aside, only run on closed MS operating systems. Let's face it, if it weren't for internal big-corp enterprise software, ASP.NET would have a much less prevalent developer base then it does now. I can't see internal enterprise projects being managed like they are OSS projects: running their own RSS feeds for packages and NuGet servers for library dependences, so I don't know how popular NuGet will become, but many of these new technologies do make my day job easier.