I've found a great solution for a shortening/butter substitute.
Take your favorite vegetable oil and FREEZE it!
It will get thicker and thicker, and eventually solidifies into something about the texture of refrigerated butter. If you work quickly with cold ingredients and utensils, you can cut it in with two knives (a pastry cutter probably wouldn't be strong enough) before it melts. (Note: Liz suggests grating it with a cheese grater, which sounds like an even better idea.)
If you just put it in the freezer for 30 minutes or a few hours, it will just be thicker colder oil, but it still works pretty well if you just quickly and lightly mix it in with a utensil or your fingertips, and avoid overmixing.
I haven't tried a pie crust yet, but it makes lovely flaky biscuits and crackers.