You have so many options Aoife - soy, rice, oat, almond, hemp, coconut are my favourites. I mix it up for variety and also because I don't like to rely too heavily on one type of plant milk. Have fun trying them all:)
I second Anne. I used Vanilla almond milk on my cereal - Nature's Gate Maple Crunch Flax. It is DIVINE! * I think I'm allergic to wheat because I feel a little drunk after I eat cereal, so probably switching to rice puffs next*
However, the pre-made tetrapacks are often a bit more convenient. I like Whole Foods Organic Unsweetened almond milk the best out of all the brands I've tried. Hemp milk is also a nice substitute, though its a bit more of an acquired taste.
Does anyone know if I can substitute Better Than Milk soymilk powder for regular powdered milk in bread recipes? I dragged the old bread machine out of the basement and my family's been loving it but so many recipes call for powdered milk.