I recently had the need to determine which delegate controls were activated on my site collection. Unfortunately I quickly discovered there was no easy way to do this in the SharePoint GUI. As such, I went searching on the Google machine, and I came across the article below. It has a great, concise overview of the problem, along with a fully flushed out PowerShell script to help you determine what you need to know.
Enjoy the post, I know I did. Many thanks to Waldek Mastykarz for writing it.
http://blog.mastykarz.nl/checking-which-delegate-controls-activated-site/