I made this bed for my daughter's doll house. It's made of chipboard (like the solid backing on the back of a pad of sketch paper). It's about 6 inches long, and 3 inches wide (12in scale).
This was the first doll bed I have ever made, so I don't have step-by-step photos or a how-to prepared. But it wasn't all that difficult to make. All you need is a headboard, a footboard, bed rails, and a mattress. I found a template for the pieces here, but I simplified the construction process.
I put the bed together using tacky glue, and covered the headboard and footboard with fabric. The mattress is made with a 3x6in sheet of chipboard and 2 layers of polyester batting covered in a simple white fabric.
The pillows are hand sewn and the blankets are simply 6x7in pieces of leftover knit material.
I think it turned out super cute, and I will definitely make another one. After all, this little girl has a brother!