If you're like me, everyone in the the house looks to you to make repairs. (How did Tim Allen do it in "Tool Time"? "Hoo, hoo!") Anyhow, the majority of these repairs can be made with duct tape, appropriate glue and clamps, nails, screws, and yes, you intuited it, galvanized or zinc-coated mending plates!
When I say mending plates, I mean that, and a combination of other more specialized building brackets and such. For example, basic mending plates have screw holes already drilled in them. They are usually shaped according to need – there's the rectangular plate, the corner angle, and the angle (either corner or "L" shaped). Then there are the other more specific application connectors: joist hangers, post caps, and beyond.
It behooves DIY'ers to keep a stock of many different shapes in the shop. You never know what you'll need for a particular job. But more than that, you'll need a pair of straight-cut tin snips (also called aviation snips). With a little creativity, you can modify a plate to mend almost anything. Recently, I've used them to repair a lawnmower, reinforce a picket fence, and brace the underside of a coffee table.