Creates a VS solution folder if it does not exist when passed a EnvDTE80.Solution2 object and a folder name.

Add-SolutionFolder

function Add-SolutionFolder {
  [CmdletBinding()]
	param(
		[Parameter(Position=0, Mandatory=$true)]
		$solution,
		[Parameter(Position=1, Mandatory=$true)]
		[string]$folderName
	)

	$exists = $false

	Foreach($project in $solution.Projects) {
		if($project.Kind.Equals([EnvDTE80.PROJECTKINDS]::vsProjectKindSolutionFolder)) 
			{
				if ($project.Name.Equals($folderName))
				{
					$exists = $true
				}
			}
		}

		if(!$exists) {
			# Create the solution folder.
			Write-Host "Creating solution folder: ", $folderName
			$parentProject = $solution.AddSolutionFolder($folderName)
		}
		else {
			Write-Host "Solution folder already exists: ", $folderName
		}
	}