For one can of sweetened condensed milk (usually 12 oz) take two cups of almond milk and bring to a simmer in a small saucepan. Depending on your tastebuds, add a teaspoon or so of agave syrup and let reduce until a cup and a half remains. Cool this mixture in the fridge and use as you would use normal sweetened condensed milk.
So far, this has worked in pumpkin pie, and my 7 layer bar recipe.
I am also experimenting with coconut milk and will let you know how that goes!
Sweetened Condensed Milk Dairy-Free Substitute
2 c almond milk
1 tsp or so agave syrup (optional)
Bring to simmer in a small saucepan. Let reduce for 15 minutes or so or until it is at the desired amount. Let cool throughly before using.