How would I display random products from a related category on another category's page. For example: On SubCategory 2 of Main Category A, randomly display 6 products from Main Category B

or a simplier example: on Main Category B's page display 6 random products below category b's products, from Main Category D.

Thanks.

Would those be consider custom category boxes?

Note: I do not want related category sideboxes. I want the related products to be below the displayed categories products.

The cross sell module seems to be for 1.3.7 not 1.3.8a anyone know if it still works?