I was trying to do a filter in Microsoft SharePoint (WSS 3.0) list where it will show me all the records in the list where the date is NULL. After number of attempts and googling I found the solution to be very simple

1) Go to modify view - (you need appropriate rights)
2) Select the date field you want to filter
3) Select is equal to
4) Leave the next text box blank

See image below

Easy….