I wrote a super-simple program in flash for our in-house use that I think might be useful to people out there all the time.
It's annoying to have to bust out the calculator whenever you're working with pixel aspect ratios, especially now that we're delivering to the web - your beautiful 16:9 NTSC project converted into flash without changing the pixel aspect ratio is squished!
This program allows you to put in your dimensions, choose whether it's 16:9 or 4:3, then it will give you the proper output dimensions for a different pixel aspect ratio, most useful when you're going to square pixels.
Here's hoping it saves time in your workflow like it has mine. Let me know if you see any bugs!