How to filter a lookup column in SharePoint 2010 ?

A very good article that made my day today :-).

http://sprider.org/2012/05/10/how-to-filter-a-lookup-column-in-sharepoint/

Useful if you cant use InfoPath 2010.

But 1 day later, I found the below method cleaner and better

http://nagendra-gunaga.blogspot.com/2012/04/how-to-implement-cascaded-dropdown-list.html