Free application or script to monitor App pool memory usage

If you don't have IIS 7 and the provider, you can use WMI. The attached script works for most of your requirements, except CPU usage. Save the below script as get-webserverapppoolstats.ps1 (or whatever you want).

You can run the script then with:

./Get-WebServerAppPoolStats.ps1 'Server1', 'Server2', 'Server3' -IntegratedAuthentication OR Get-Content servers.txt | ./Get-WebServerAppPoolStats.ps1 -IntegratedAuthentication

param (
    $webserver = $null,
    $username,
    $password,
    [switch]$IntegratedAuthentication)

BEGIN
{
    $path = $MyInvocation.MyCommand.Path

    if ($webserver -ne $null)
    {
        if ($IntegratedAuthentication)
        {
            $webserver | &$path -IntegratedAuthentication
        }
        else
        {
            $webserver | &$path -username $username -password $password
        }
    }
    $OFS = ', '
    $Fields = 'CommandLine', 'Name', 'CreationDate', 'ProcessID', 'WorkingSetSize', 'ThreadCount', 'PageFileUsage', 'PageFaults' 

    $query = @"
    Select $fields
    From Win32_Process
    Where name = 'w3wp.exe'
"@

    $AppPool =  @{Name='Application Pool';Expression={($_.commandline).split(' ')[-1]}}
    $Process = @{Name='Process';Expression={$_.name}}
    $RunningSince = @{Name='Running since';Expression={[System.Management.ManagementDateTimeconverter]::ToDateTime($_.creationdate)}}
    $Memory = @{Name='Memory Used';Expression={'{0:#,#}' -f $_.WorkingSetSize}}
    $Threads = @{Name='Thread Count';Expression={$_.threadcount}}
    $PageFile = @{Name='Page File Size';Expression={'{0:#,#}' -f $_.pagefileusage}}
    $PageFaults = @{Name='Page Faults';Expression={'{0:#,#}' -f $_.pagefaults}} 
}

PROCESS
{
    $server = $_ 

    if ($server -ne $null)
    {
        if ($IntegratedAuthentication)
        {   
            $result = Get-WmiObject -Query $query -ComputerName $server
        }
        else
        {
            $securepassword = ConvertTo-SecureString $password -AsPlainText -Force
            $cred = New-Object System.Management.Automation.PSCredential -ArgumentList $username, $securepassword

            $result = Get-WmiObject -Query $query -ComputerName $server -Credential $cred 

        }
        $Server = @{Name='Server';Expression={$server}}
        $result | Select-Object $Server, $AppPool, $Process, $RunningSince, $Memory, $Threads, $PageFile, $pageFaults
    }
}

Yes powershell can do this with the new powershell provider for IIS it's easy. Here are some of the examples from the run time data walkthru's provided:

AppPool State

PS IIS:\> cd AppPools
PS IIS:\AppPools> Get-WebItemState DemoAppPool
Started
PS IIS:\AppPools> Stop-WebItem DemoAppPool
PS IIS:\AppPools> Get-WebItemState DemoAppPool
Stopped

Worker Processes and Requests The get-process cmdlet doesn't help you figuring out which Application Pool a particular worker process is serving. This can be easily done however:

PS IIS:\AppPools> dir DefaultAppPool\WorkerProcesses

               processId                  Handles                    state StartTime
               ---------                  -------                    
                   6612                      326                        1 3/28/2008 12:20:27 PM

note that once you have the PID regular

   get-process -id pid

will tell you the memory usage