One thing has saved my life this summer, seeing as we don't have a swingset yet for the kids. This:
We bought this table as a present for Liz on her birthday. It was by far the best thing we could have gotten her. All of the kids enjoy it and since we've used up all the sand, it has just become a water table. The things I like about this table are: the umbrella (a necessity for those of us with no trees!), the lid, and it is sturdy (it doesn't collapse even when climbed on!). Most of all, it is versatile. First, we used it with sand and water, then just water, and come fall, I plan on filling it with rice and keeping it on the porch (or basement) for cool weather play.
The hit right now is ice cubes! All day I fill trays of ice cubes and they play with them in it until they melt. Lots of fun. And sometimes, I make "surprise" trays:
This one is filled with trinkets from our "junk" drawer.
This is an "ice mountain" with a dinosaur waiting to be excavated.
As much as I love the water table, you could do this with a big, shallow sterlite container. And we have done that before, but invariably, one of the pets ends up in it! And, you could get cheap funnels, measuring cups, and other containers from the dollar store for more play (which could also be used with sand or rice).