I am a huge fan of the do it yourself kind of kids fun.
One great idea is to take a large box or two in your garage or basement or out of the way and put things you might ordinarily recycle in them. Toilet paper and towel rolls, scoops from detergent, yogurt and cottage cheese containers, some packing wrap or peanuts from a gift you got, old clothes pins, film roll canisters, bits of string and yarn and fabric, anything really. You can even put pieces of cardboard or boxes in it. You just keep tossing stuff in it until it is full. It becomes a creativity station. You can add paints and glue, etc, depending on age, and have kids go wild making something of their own imagination. I've seen kids make robots and toys or forts and puppets and puppet theater. You don't even have to give them any directions just tell them that this is what they have and they can make whatever they want as long as it is safe. They may need a bit of prompting the first time but it will quickly become a favorite activity. The more the merrier and you can even contact local industry to see if they have scraps and recyclables you could use. Bits of old keyboards and computers are great, old phone pieces, some wood, screws and bolts, etc. It is a really fun activity to do a couple of times a year, when you have lots of stuff.
Another fun recycling activity is to keep the cardboard that comes in the calendars. It is the size of the calendar. You can make a wreath from it. In fall, you collect leaves and cones and other dried things from the ground in fall and glue them on to a circle you've cut out of the cardboard. Younger kids may need an adult to do the hot glue gun. In winter, you can do greenery. In spring, you can collect flowers and flatten them in a book and then glue them on with just elmer's type glue. In summer, it could be sand and shells.
For younger kids, dried food collages are inexpensive and fun. You just cut a shape out of cardboard or tag board (the cheapest poster board from the art store) and they can use elmer's type glue to make collages that are realistic or abstract. The more patient kids could study and make mandalas. You can also just use paper you have around the house, like the cereal boxes turned inside out.(Google mandalas for more info).
Make bubbles and bubble wands. You can make your own soap bubble recipe from just glycerin and soap. You can buy copper wire at the hardware store (and wire cutters if you don't have them) and you can give each child a section of wire to form into a shape for making bubbles. Or, use you cooking utensils and different size bowls to see what happens. Bubbles are best done on a shady day. Kids love this and copper wire is cheap and you get a big roll.
I also like to make clay and dough and do some sculpting.
Go the link below and you will find recipes for clay as well as links for recipes for other at home crafts, like soap bubbles. The basic bubble recipe with glycerin and dish soap is the best. Glycerin holds the bubble together. It is very inexpensive and can be found at most pharmacies. I've always found it near the bar soaps.
http://www.recipegoldmine.com/childclay/childclay.html
Have fun!