Downy Wrinkle Releaser. It's the best. It's $6.99 or so for a bottle, kind of pricey, but I love it and use it along with ironing, it makes ironing so much easier. But you can actually not even have to iron if you use it, a lot of clothes you can just spray it on, smooth out the wrinkles and let the garment hang up and it's fine and all the wrinkles come out. Zero ironing.
Love it!!!! You can buy it at Target or sometimes Walmart carries it. It's in the laundry aisle by the pretreaters usually.
Also drugstore.com sells it. It used to be manufactured by P&G but they sold the right to another company, but you should still be able to find in stores. I turn the garments inside out and spray them when I use it.
On some types of materials it might leave little water dots, so you just have to learn which fabrics it works with and which is doesn't. You know the same items where you get a tiny water dot and it looks funny, well you know you can't use the spray on that type of material, basically rayon type materials are problematic with water splotches in general. Just FYI.
Works great on cottons though! Some people are frugal and make their own spray with water and fabric softener. You can google that. But I completely trust Downy, I rave about it, have been using it about 9 years at least!~