Web Part to display the related items to the current item. Using a technique from a SharePoint Hero named Todd Bleeker (
Todd Bleeker's Blog) you can put the standard SharePoint Display, Edit and New Forms into edit mode and add web parts to them. Adding the Related Web Part provides a way to visualize the relationship to the current item via a lookup field in a standard form. In other words, you can see all the related children right in the parent! 'Add New' links provide way to add children (related items) to the current item.
This connection between the parent and child can be made easier using the Enhanced Lookup Column because the lookup column will be provided with a default value. If the web part is dropped on a page without an ID in the querystring parameters, the selected view will be shown with an additional Group By the selected lookup field.