Virto Cross Site & Cascaded Lookup is a powerful feature allowing referencing and cross-referencing existing data in SharePoint Lists across current site or site collections. It also allows SharePoint users to access list items from across your Site Collections automatically deleting duplicated values. Moreover, Virto Lookup feature supports cascaded look up functionality. It allows cross-referencing existing data from a list or site within the same site collection and then applies filters to reduce the number of options presented in the drop down menu of your lookup field.
||Free to try
||Microsoft SharePoint Release 2010