Set item field to external url

Set-ItemFieldToExternalLink.ps1

function Set-ItemFieldToExternalLink{
    [CmdletBinding()]
    param(
        [Parameter(Position=0, Mandatory=$true, ValueFromPipeline=$true)]
        [ValidateNotNullOrEmpty()]
        [Sitecore.Data.Items.Item]$Item,

        [Parameter(Position=1, Mandatory=$true)]
        [ValidateNotNullOrEmpty()]
        [string]$FieldName,

        [Parameter(Position=2, Mandatory=$true)]
        [ValidateNotNullOrEmpty()]
        [string]$Url,

        [Parameter(Position=3)]
        [string]$Title = ""
        )

  $Item.Editing.BeginEdit();
  [Sitecore.Data.Fields.LinkField]$field = $Item.Fields[$FieldName]
  $field.Text = $Title
  $field.Title = $Title
  $field.LinkType = "external"
  $field.Url = $Url
  $item.Editing.EndEdit() | Out-Null
}

#Example- assuming the "home" item has a general link field named "GeneralField" 
Get-Item master:\content\home | Set-ItemFieldToExternalLink -FieldName "GeneralLink" -Url "http://www.cognifide.com" -Title "CognifideWebsite"