I use Zoop as a foundation along Drupal for damn near every app I write now.
I think the best example I have is Bid Master, a sophisticated search term valuation system that currently manages over 300K search terms based on real time market conditions. Zoop and Drupal helped to keep the focus on the core application functionality. I've started a Drupal and Zoop tutorial but, with Bid Master going live, I've been swamped. I swear, I'll finish the tut. soon!