Pregnancy will calculate a due date (or reverse look-up).
http://users.adam.com.au/paulwh/_Pages/misc.html (scroll down)
Added here: http://www.portablefreeware.com/index.php?id=2549
Pregnancy from L2 Software
Re: Pregnancy from L2 Software
Unique!
Re: Pregnancy from L2 Software
EDIT: ahh, It's donationware, not freeware; found out too late, sorry! However, still a nice piece of software!