What program are you using to do the sizing and cripping? If you use the right program they shouldn't look distorted or squishy. Photoshop (expensive) or Photoshop Elements (not as expensive) should both do the trick. There is also Gimp, a free program to download or I think there is an online one. I'll have to check on that one.
Yep, here it is:
http://pixlr.com/
It will be difficult to make the pictures that are wider than tall come out square. Might need some creativity with that part.