Additionally you can choose to keep the start page open when loading a project. There's a check box below the projects list for that.
(Tested in VS2010, VS2012, VS2013, VS2015)
In current versions, you can also use the Quick Launch (Ctrl+Q) to search for the command
(Just type "Start Page" in Quick Launch)
Visual Studio 2017
There's a menu item File -> Start Page
You can configure the behavior of the IDE on startup via Tools -> Options -> Environment -> Startup.
In Visual Studio 2017, the start page will open automatically when the solution is closed. As far as I know, this cannot be changed directly in the IDE but there's an extension that adds that feature. See this question on SO and this VSIX-Extension (but this will disable the start page completely - if you try to open it manually, it will be immediately closed automatically)
It used to be automatic in VS2008 - Anything you had open outside of any solution/project (including the start page) would close when you opened a project/solution, then when closed that product/solution it went back to what was open before. That is how it should work, they broke it in VS2010. So all the prior VS users searching for the answer - there is none - technology continues to regress.