This powershell script gets all of the values is a field in a sharepoint list using the field name
if(-not(Get-PSSnapin | where { $_.Name -eq "Microsoft.SharePoint.PowerShell"}))
{
Add-PSSnapin Microsoft.SharePoint.PowerShell;
}
$site = Get-SPweb "http://portal.opwftg.com/sites/OPWSS/Teams/OCM"
$mList=$site.Lists["PublicFolderExport"]
$i = 0
foreach($f in $mList.Items)
{
$f["EmailSubject"].ToString()
}