I often set DS up at the kitchen table while I am cooking and stuff. I still need to be in the room otherwise paint ends up everywhere but he will usually play for quite a while. We don't tend to do the kind of crafts where things have to be stuck in the right places to make a finished object.
Playdough, we make our own with cutters rolling pins, plastic cutlery and anything else we can press into it to make patterns.
Threading cherios type cereal onto a shoelace (OK we still have more eating than threading at 3)
Painting, we have different thickness brushes, old tooth brushes, a few sponges and or course fingers. We also like to put a couple of blobs on a baking tray for the kids to mix and smear around. Sometimes we put a sheet of paper on top to make a print. Often we don't bother.
Glueing, I used to keep a small box of shapes ready cut out to hand out with a glue stick. Now DS prefers to cut his own shapes so I keep old wrapping paper and junk mail with pictures I think he will like. This is probably his favourite activity.
In terms of making things we've decorated containers with a plastic lid and cut a slot in the lid to make a money box, decorated a cereal box to keep all the artwork in.