Auto select file in Solution Explorer from its open tab

I don't know if you can do it on-demand, but you can enable the option "Track Active Item in Solution Explorer" (Tools->Options->Projects and Solutions->General) which will always select the active tab item in the solution explorer.

Another option is to bind 'View.TrackActivityInSolutionExplorer' to a keyboard short-cut, which is the same as 'Tools-->Options-->Projects and Solutions-->Track Active Item in Solution Explorer'

If you activate the short-cut twice the file is selected in the solution explorer, and the tracking is disabled again.

Visual Studio 2013+

There is now a feature built in to the VS2013 solution explorer called Sync with Active Document. The icon is two arrows in the solution explorer, and has the hotkey Ctrl + [, S to show the current document in the solution explorer. Does not enable the automatic setting mentioned above, and only happens once.