AbleCommerce Shopping Cart Software

Has anyone added a quantity box next to the add to cart button on the category page?

Try this:
Login as admin on your site
Browse to the category page
Scroll down and change mode to Edit Page
Change the content scriplet to "Category Grid with Basket Options"
Click Apply

Here is a reference page with the provided category page layouts: http://help.ablecommerce.com/mergedProj ... amples.htm

You can also do this for all of your categories at once from the admin side. For this navigate to the Admin->Website->Themes and Display Pages and then for Category Display Page option select Category Grid (Deep Item Display) With Add To Basket (CategoryGrid3.aspx for it.