Function to list packages installed in a Sitecore instance.

Get-PackageHistory.ps1

<#
    Adapted from the Package History module found here:
    https://marketplace.sitecore.net/en/Modules/PackageHistory.aspx
#>

function Get-PackageHistory {
    $packageHistoryPath = "/sitecore/system/Packages/Installation history"
    $packageRegistrationTemplateId = "{22A11D20-5F1D-4216-BF3F-18C016F1F98E}"
    $coreDb = Get-Database -Name "core"
    $historyItem = $coreDb.GetItem($packageHistoryPath)
    if($historyItem) {
        
        $props = @{
            Property = @(
                "Name", "ID", 
                "Package Name", "Package Version", 
                "Package Author", "Package Publisher", 
                "Package ReadMe", "Package Revision",
                "Package ID"
            )
        }
        
        foreach($installItem in $historyItem.Axes.GetDescendants()) {
            if($installItem.Template.ID -eq $packageRegistrationTemplateId) {
                
               Get-Item core:\ -id $installItem.ID | Select-Object @props
            }
        }
    }
}