Obtener un listado de Webs, Listas y Librerías de una web application

Para ver el listado de un SiteCollection

Get-SPSiteInventory -Url http://spsite –SiteCollection

Para ver el listado de un web application

Get-SPSiteInventory -Url http://spwebapp –WebApplication

La función completa

function Get-SPSiteInventory {
Param(
[string]$Url,
[switch]$SiteCollection,
[switch]$WebApplication
)
Start-SPAssignment -Global
	if ($SiteCollection) {
		$site = Get-SPSite $Url
		$allWebs = $site.allwebs
		foreach ($spweb in $allWebs) {
			" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "
			$spweb.Url
			$spweb.Lists | select Title, BaseType
			$spweb.dispose()
		}
		$site.dispose()
	} 
	elseif ($WebApplication) {
		$wa = Get-SPWebApplication $Url
		$allSites = $wa | Get-SPSite -Limit all
		foreach ($spsite in $allSites) {
			$allWebs = $spsite.allwebs
			foreach ($spweb in $allWebs) {
			" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "
			$spweb.Url
			$spweb.Lists | select Title, BaseType
			$spweb.dispose()
			}
		}
	}
Stop-SPAssignment -Global
}

Fuente: http://sharepointryan.com/2012/01/25/get-a-web-list-and-library-inventory-using-powershell/