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tapioca pudding?

Great minds think alike, judging by first comment.
My second suggestion would be to make a cream of broccoli & cheese soup or any other type of dairy based soup.

Homemade chai tea.

Pudding was my first thought too. Homemade pudding is sooooo good (way better than the boxed mixes), and there are good recipes out there for about any flavor imaginable. Take it a step further, if you like, and use that pudding in a pie, a trifle, etc. Cream-based soups are also a good suggestion, and something you could do now and freeze for later. Higher fat milks work well in drinks too, such as smoothies and milkshakes. Beyond that...l don't know...lots of cereal?

Try to make the curdled Dulce de Leche too... it's different and tangier, but really good.

http://www.univision.com/content/content.jhtml?cid=489201

The recipe is in Spanish, but let me know if you're interested and I can translate if necessary.

Make ice cream for sure! Then take the ice cream and make milk shakes.
Sausage and gravy--I've used 2% and it's just fine.

rice pudding bread pudding a big batch of mac and cheese you can freeze.

for the benefit of dbcurrie and all those interested... here goes the Dulce de Leche Cortada recipe in English. This recipe was taken from the Univision.com site and comes from chef Jaime Vazquez from rest. La Carreta in Miami, FL. I have eaten thsi dessert many, many times when I was growing up, but I have never made this recipe in particular...

DULCE DE LECHE CORTADA

Ingredients:
2 liters of milk
1 lb sugar
4 egg yolks
1 green lime or limon criollo – you’ll use both the rind and the juice
1 cinnamon stick
3 drops of vanilla extract
A pinch of salt

Mix well the milk and sugar. Add the egg yolks and the juice of ½ lemon. When everything is well blended, pass thru a fine sieve.

Add the vanilla, salt, cinnamon and the zest of ½ lemon. Let the mixture rest about 30 mins. (If you're not too fond of lemon zest in recipes... just cut a few pieces of rind and let them steep in the mixture while it rests... the flavor will be in the mixture without the pieces of zest.)

Place on top of high heat until it just starts to boil. Reduce the heat to medium and stir once in a while. When the mixture has turned golden and it develops some sort of syrup, it’s done.

Remove from heat and transfer to the fridge to cool. This dessert is best served cold.

This dessert is very sweet, so it’s traditionally served with pieces of cheese to cut the sweetness – cheddar cheese or white cheese are very popular.

You can freeze milk.

I second what CJ said. Measure into cups or half-cups and freeze. Take some home and use in your own baking or cooking. Also the puddings, hot cereal and muesli (if he eats such things), ice milks and sorbets, cherry soup or other fruit soups, other cream soups, mashed potatoes, cakes (instead of water), cream gravy...... Milk separates a bit when you thaw it so not all uses would be as good as with fresh, but you can certainly do enough. I learned all kinds of tricks for slipping milk into things for its nutritional value when a friend was caring for an elderly family member. For puddings, consider unusual ones such as tapioca, or the classic baked rice pudding that nobody does anymore (just stirring rice, sugar, spices, and dried fruit if you like it, into a LOT of milk and baking slowly), indian pudding (molasses and cornmeal and sugar and spice), and so forth. Custard pies. Custard sauce over summer fruits.

And stop buying your dad so much milk!