FindProjectsUsingVariableSet.ps1

#The -IncludeUsage switch will populate $VariableSet.Usage with the name of the projects using the LVS
#If -IncludeUsage is not passed, .usage will always be empty

Set-OctopusConnectionInfo -Server http://OctoServer -ApiKey API-XXX

$VariableSets = Get-OctopusVariableSet -LibrarySetName * -IncludeUsage

foreach($VariableSet in $VariableSets){
    Write-Output "`nVariable set [$($VariableSet.LibraryVariableSetName)] is being used by projects"

    foreach($project in $VariableSet.Usage){
    "--$project"
    }
}