From http://blogs.technet.com/b/nzdse/archive/2011/12/11/powershell-script-retrieve-specific-event-id-s-from-event-log-on-multiple-computers.aspx

GetLogonEvents.ps1

    #requires -version 2.0
    <#
    author: Johan Vosloo
    date: 24/11/2011
    purpose: Retrieve event id’s from multiple machines and add to a CSV file.
    #>
    Try
        {
        $servers=get-content c:\scripts\servers.txt
       $date=(Get-Date).AddDays(-7)
       foreach ($server in $servers)
           {
           if (test-connection $server -quiet)
               {
               $arr1+=get-eventlog -logname system -cn $server -after $date | ?{$_.eventid -eq "21" -or $_.eventid -eq "4201"} | select MachineName,EventID,EntryType,Message
               $arr2+=get-eventlog -logname application -cn $server -after $date | ?{$_.eventid -eq "902" -or $_.eventid -eq "1003"} | select MachineName,EventID,EntryType,Message
               $arr3+=get-eventlog -logname "windows powershell" -cn $server -after $date | ?{$_.eventid -eq "4004"} | select MachineName,EventID,EntryType,Message
               }
           }
           if ($arr1)
               {$arr1 | export-csv c:\scripts\sysoutput.csv -notypeinformation}
           else
               {"No matching system log events found..."}
           if ($arr2)
               {$arr2 | export-csv c:\scripts\appoutput.csv -notypeinformation}
           else
               {"No matching application log events found..."}
           if ($arr3)
               {$arr3 | export-csv c:\scripts\psoutput.csv -notypeinformation}
           else
               {"No matching powershell log events found..."}
       }
   Catch
       {
       "An error occurred"
       }