Most recipes I have that use condensed milk call for full 14 oz can.
I've ben enjoying the chai mix here: http://food52.com/recipes....
Vietnamese iced coffee - only uses a couple of tablespoons of condensed milk per glass, but it's a great warm weather dessert for a group, easily made in a jug to pour over ice (sliced mango, berries, etc. are nice with it.) Assuming you don't happen to have a Vietnamese metal coffee filter lying around - I just use my old-school stovetop espresso maker: http://whiteonricecouple.com/recipes/vietnamese-iced-coffe-recipe/
Bake it and make dulce de leche!
Other than eating it straight off the spoon? Use it to sweeten coffee or tea, drizzled over berries, cake, bread pudding, french toast, mixed with heavy cream to make a no-churn ice cream, hello dolly bars, rice pudding, etc.
No-churn ice cream:
Spread it on toast. Yumm!
It's a no brainer fmacmac, though it may be an extension of Ida Yu's answer, but I would make a classic Hungry Monk Banoffi Pie, perhaps the greatest desert the modern World has ever known. You could scale it down to make a smaller one if you don't have enough of the condensed milk left over. Here's a link to the original recipe:
in addition to all the good answers - no bake or chocolate biscuit cake (British eg Hugh Fearnly Whittingstall recipe), pumpkin pies or tarts, with Sriracha for a creamy hot sauce
Nigella has a great ice cream that does not require using an ice cream maker: http://www.nigella.com...
You can add it to corn kernals and process to use in Mexican Lasagna. The now creamed corn can takes the place of Béchamel just add a variety of peppers and build accordingly to taste.
Unbelievable as it may sound condensed mil (plus cream and other ingredients of you choice) makes wonderful ice cream without a machine (or much time or effort or having to mash the stuff as it freezes) - so I wrote an ebook about it!