Zen Cart Save for Later is a mod that allows your customers to set aside items in their cart for later purchase. This way, they don't lose track of the items entirely (especially important for attribute-heavy items), and you close them on a smaller sale (the remaining items in their cart) without losing the possibility of selling the other items later on. Amazon has used this mechanism successfully, and I hope you'll be able to as well.
The Save for Later Report shows you who's using Save for Later and what the most commonly saved items are.
For more information, please visit this product's webpage.