Powershell function for Sharepoint 2010 to get a taxonomy term using a spsite object, a field name and label. In this scenario we pass back the label / value pair however you can easily modify to return the term object.

gettaxonomyterm.ps1

Function GetTaxonomyTerm($spsite, $field, $label)
{
  Write-Host "Getting term for $($label)..."
	$taxonomySession = Get-SPTaxonomySession -Site $spsite
	$taxonomyField = $spsite.RootWeb.Fields.GetField($field)
	
	$termStoreID = $taxonomyField.SspId	
	$termStore = $taxonomySession.TermStores[$termStoreID]	
	
	$termsetID = $taxonomyField.TermSetId	
	$termset = $termStore.GetTermSet($termsetID)
	
	$term = $termset.GetTerms( $label, $true)
	
	return [string] $term[0].Name +"|"+$term[0].Id	
}