PowerShell script in setting up multiple SharePoint Alerts

Here is a basic outline of creating an alert using powershell. Combine this with some powershell that iterates through the sites / lists you are hoping to target and you have yourself a good start.

$SPsite = Get-SPSite "http://SharePointSite.com"
$SPweb=$SPsite.Rootweb 
$SPlist=$SPweb.lists["Shared documents"] 
$SPuser = $SPweb.EnsureUser('Domain\Salaudeen') 
$SPnewAlert = $SPuser.Alerts.Add() 
$SPnewAlert.Title = "My Custom Alert"
$SPnewAlert.AlertType=[Microsoft.SharePoint.SPAlertType]::List 
$SPnewAlert.List = $SPlist
$SPnewAlert.DeliveryChannels = [Microsoft.SharePoint.SPAlertDeliveryChannels]::Email 
$SPnewAlert.EventType = [Microsoft.SharePoint.SPEventType]::Add 
$SPnewAlert.AlertFrequency = [Microsoft.SharePoint.SPAlertFrequency]::Immediate 
$SPnewAlert.Update() 
$SPweb.Dispose() 
$SPSite.Dispose() 

Read more: http://www.sharepointdiary.com/2011/11/managing-alerts-using-powershell.html#ixzz2OaCHGyYf