Thanks, all. This gives me lots of useful dairy-free options! Starting a bake-a-thon today, since we're snowed in.

I use Spectrum's buttery sticks in place of butter in lots of recipes; I don't notice a big difference (vs butter) in cookies and most cakes. I've used palm shortening in cookies and pie crusts in place of butter. It smells strong out of the can, but once it's baked, I don't notice the odor anymore. I'm not a big lard fan for health reasons, and because I always notice a meaty taste and smell when I bake with it.

If you are making pie crusts, lard (rendered suet) makes the best crust. I have never used lard in any other baking (though I use it in making rillettes, when I can not get duck fat), except suet in mince meat, but that is another story. There are a few new products out there, which you are more likely to find in a natural food store. Palm shortening, under new processes, is no longer a horrible fat. In fact, it is considered a good shortening to use and is being replaced in many organic recipes. I would go that route first. . . it is healthier than lard.

Other good cooking fats and oils to consider: coconut oil, palm oil, vegan "buttery sticks" from Earth Balance. I use the buttery sticks in place of butter for cookies, pie crusts, biscuits, scones, etc., and it works just the same as butter. Coconut oil can also be used to replace butter in baked goods, thought the result is less like butter and more like an extra-fatty oil. Also, consider replacing the butter in your quick breads, muffins, and cakes with canola oil. It will change the texture and crumb slightly, but most people don't know the difference. I made my wedding cake with canola oil and no butter:
http://www.food52.com/recipes/8634_chocolate_wedding_cake_glutenfreedairyfreesoyfree

stephskitchen, suet and lard are very similar to each other and i included a cooking fat breakdown graph from wikipedia below to show their differences, which also compares several other cooking fats. many recipes use lard over butter because it makes a flakier pie crust, for example, and suet and lard would probably function interchangeably to each other. however, be aware of the differing smoke points, as this could affect how you wish to cook with them.

also, as I have suggested to other people looking for non-dairy baking alternatives, you might try the "I Can't Believe It's Not Butter" sticks, which you can use in baking just like butter, except it has no trans fats and has half the saturated fat of regular butter and has no dairy, which would be good for your son. Most people can't tell the difference in a baked good unless you tell them. i hope this helps!