Build a toddler size tee pee bed using the free woodworking plans at the link. It is an easier project than you might think at first.
Build this simple twin bed using this free step-by-step tutorial. Plan requires only off the shelf lumber and minimal tools.
Why build a basic bed when you could build this house frame toddlers bed. This one is sized for a crib mattress but you could adjust the width and length to fit a single bed too. Free plans at the link.
How fun! Build this kitty headboard as part of a twin trundle bed. Perfect for having a sleep over, then tuck it away when you don’t need it. Free downloadable plans at the link.