Implemented a database-rule-driven product configurator, as part of a migration of the Rig-A-Lite site to Drupal 7. Rig-A-Lite provides lighting solutions for hazardous environments, such as light fixtures for off-shore oil rigs. Their old product configurator did not enforce legal configuration choices - such as which ballasts require fuse blocks, or are not available with metal halide lamps, for example - which caused order processing aggravation for their worldwide sales reps and customers.
The configurator is iframe'd into Drupal, leveraging the company's old sophisticated full-custom PHP/MySQL/JQuery CMS backend to populate its new Drupal front end. The new rules data is edited in a valid-configurations Excel table, and imported into the CMS, to drive the product configurator user interface.
Last I knew, most products hadn't been converted to use the new configurator. That was a design feature, that the new system would allow them to use both old and new product configurators side by side, as they gradually converted products.