I have a play structure that has a slide, playhouse, 2 swings and a pool that can be attached to the bottom of the slide but I keep it separate for safety reasons. I have 2 normal swings, 2 baby swings and a tire swing that I rotate on the structure depending on the ages of the kids I have. This is by far their favourite of the toys.
I also have a diego ship, a smaller slide and a kids sized picnic table that are out all summer.
Than I have ride on cars, baby strollers and dolls, lawnmower that blows bubbles and kid sized chairs. I have a toy box that I keep smaller toys in but they don't really play with them that often as they are similar to the indoor toys so they want to play with the larger things. I also have an assortment of balls of different sizes. Chalk and chalk rakes are a hit too.
I used to have a water table but they never played with it so we just use the pool or go to the splash park. I don't have sand in my yard but we play at the sandy park near us often.
This summer I will probably bring out the indoor trampoline to get more use out of it. We also do a lot of fun summer activities that I will bring things outdoor for. Their favourite activity last summer was a car wash...I gave them a bucket of warm soapy water, put them in bathing suits, dragged all the big cars out to the driveway and let them go to town!