This module was born out of a BoF at Drupalcon DC with members of the Churches Drupal group, the Ubercart maintainers, and Commerce Guys. The goal was to develop a suite of modules useful for allowing churches and other non-profit organizations to accept donations using Ubercart on Drupal 6. This resulted in this list of specifications being approved and funded by the Churches group.
The UC Add to Cart Tweaks product feature allows you to alter ways the add to cart form behaves for any product in your Ubercart store. The current tweaks provided allow you to empty the shopping cart when the add to cart form is submitted and to alter the add to cart redirect URL. Extra integration with Ubercart's product classes interface allows you to set default Add to Cart Tweaks on every product created of any given product class.
See the project page for more information. Bug reports and feature requests should be posted in this project's issue tracker.