For cupcakes you'll find they work best if you stand each of your cupcake cases in a yorkshire pudding (muffin) tin. If you don't then the paper cases can sag.

 

These come in various sizes - above is the classic size, you can also get mini tins, and giant tins.

The above are metal, but you can also get these in silicone which are fine - although you'll want to put them onto a metal tray to put them in the oven or they have a tendancy to slump.

You can also get individual silicone cake cases, and although I have some, I'm not sure why as peeling the paper case from a cupcake or muffin is a pleasure whereas chasing round after my guests to retrieve the silicone ones really isn't. The one benefit is you can use them for wet ingredients like mini jellies that wouldn't really work in a cake case.