Where to start, I love ready made puff pastry!!
As a base for a million kinds of tarts/pizzas - roll out to the size of a baking sheet, score about 2cm from the edge on all sides, spread base with something (tomato paste, pesto, jarred pasta sauce, creme fraiche, olive tapende, etc), arrange anything you like on top (sliced veg (courgettes, aubergine, peppers, tomatoes particularly good), anchovies, olives, sun dried tomatoes, fried onions, slices of ham, pepperoni, bacon) and then bake for about 15 minutes. Take out of the oven and top with cheese (anything that will melt nicely works fine - mozzarella, gruyere, mild cheddar, blue cheese, brie, taleggio etc). Place back in oven till the cheese melts and the edges are brown. This is great for a kid's activity too because the pastry cooks so fast so it's ready really soon after kids make their own pizzas.
You can do the same but with sweet things to make desserts - slices of apple/peach/nectarine/plum/etc dusted with sugar and spice (like so: thepioneerwoman.com/cooking/2009/05/quick-easy-and-yummy-apple-tart/). If you make pie filling and fold over the puff pastry you'll get turnovers or hand pies (recipe here for fried ones like McD's: www.evilshenanigans.com/2010/10/apple-fried-pies-made-with-puff-pastry/)
Make your own sausage rolls - take sausages out of their casings, mix with minced onion/mustard powder/garlic/herbs if you like, spread inside of puff pastry with grain mustard (optional), brush opposite edges of pastry with water to stick and roll up into long sausage. Snip into sausage roll size with scissors and place seam side down on a baking tray, brush top with egg, in oven till tops are dark golden and pastry is puffed up.
And there's always making things in pastry for dinner - salmon, cod, beef etc.