I recently had to improvise some network scanning using PowerShell. The security guys got somewhat excited, so I decided to upload these snippets.
I think all of them require PowerShell v2+

Checking ping for one IP address

Test-Connection $target -count 1 -quiet

Checking if a TCP port is listening

function TryOpen-TCPPort([string]$target,[int]$port){
 try{
  $socket = new-object System.Net.Sockets.TcpClient
  $socket.Connect($target,$port)
  $socket.Close()
  return $true
 }catch{return $false}
}

Scanning a list of addresses for predefined ports

function Map-Ports{
 param(
  [string[]]$targets,
  [int[]]$tcpPorts
 )

 $targets | %{
 $target = $_
 $ret = new-object object
 $ret | Add-Member NoteProperty 'Name' $_
 $ret | Add-Member NoteProperty 'IP' $null
 $ret | Add-Member NoteProperty 'HasPing' $null
 $tcpPorts | %{$ret | Add-Member NoteProperty "TCP$_" $null}
  $ip=$null
 try{
  $ip=[System.Net.Dns]::Resolve($target).AddressList[0].IPAddressToString
 }catch [Net.Sockets.SocketException]{}
 $ret.IP=$ip
  if($ip){
  $ret.HasPing = (Test-Connection $ip -Quiet -Count 1)
  $tcpPorts | %{$ret."TCP$_" = (TryOpen-TCPPort $ip $_)}
 }
 $ret
}
}

Scanning some subnet for web servers

Map-Ports -targets ((1..254) | %{"10.0.0.$_"}) -tcpPorts 80,443

Scanning my immediate subnet for common MS ports

# Fabricate IP Addresses
function Fabricate-IPAddress([string]$header,[int]$levels=0){
 $queue=@($header)
 while($levels--){
  $newQueue = $queue | %{$q=$_;(1..254) | %{"$q.$_"}}
  $queue = $newQueue
 }
 $queue
}

# Scan Immediate Addresses
function Scan-MySubnet{
 $myIps = gwmi win32_networkAdapterConfiguration -fi 'IPEnabled=True' | %{
  for($i=0;$i -lt $_.IPAddress.length;$i++){
   $_ | select `
    @{Name='IP';Expression={[System.Net.IPAddress]($_.IPAddress[$i])}},
    @{Name='Subnet';Expression={[System.Net.IPAddress]($_.IPSubnet[$i])}}
  }
 }
  $myIPs | %{
  [int]$levels=0;
  # Worst range calculation ever, but it works for standard subnets
  switch($_.Subnet){
   '225.255.255.0' {$levels=1}
   '225.255.0.0' {$levels=2}
   '225.0.0.0' {$levels=3}
   default {Write-Error 'Too lazy to calculate range';continue;}
  }
  $header = ($_.IP.GetAddressBytes()[1..(4-$levels)]) -join '.'
  Fabricate-IPAddress $header $levels
 }
}

Map-Ports -targets (Scan-MySubnet) -tcpPorts 135,445

Testing a web page on a server

function Get-WebResponseCode([uri]$url,[switch]$UseDefaultCredentials){
 $req = [System.Net.WebRequest]::Create($url)
 $req.UseDefaultCredentials=$UseDefaultCredentials
 # Avoid downloading the whole page
 $req.Method='HEAD'
 try{$resp=$req.GetResponse()}
 catch [System.Net.WebException]{$resp=$_.Exception.Response}
 '{0}: {1}' -f ([int]$resp.StatusCode),$resp.StatusDescription
}

Testing common webpages on a server

function Test-WebPages{
 param(
 [string[]]$targets,
 [uri[]]$paths,
 [string[]]$schemes='http',
 [switch]$UseDefaultCredentials
 )

 $targets | %{
  Write-Progress 'Testing Servers' $_ -Id 1
  $target = $_
  $schemes | %{
   Write-Progress 'Testing Schemes' $_ -Id 2
   $scheme = $_
   $ret = $new-object object
   $ret | Add-Member NoteProperty 'Name' $target
   $ret | Add-Member NoteProperty 'Scheme' $scheme
   $paths | %{$ret | Add-Member NoteProperty $_ $null}

   $pu = new-object uri ([uri]"${scheme}://$target")
   $paths | %{
    $u = new-object uri $pu,$_
    Write-Progress 'Testing Url' $u -Id 3
    $ret.$_ = Get-WebResponseCode $u -UseDefaultCredentials:$UseDefaultCredentials

  }
  $ret
 }
}

Test-WebPages 'SharePointDev','ExchangeCAS','AnotherServer' -paths '/','/owa','/sites' -schemes 'http','https' -UseDefaultCredentials