Here's a clever idea. Need a platform for your mattress? And perhaps some storage? Reuse some shelves from Ikea to do it. Use two Ikea Expedit 5x1 shelving units into a platform storage bed along with two sheets of MDF, a 4x4-inch post, and a few floor protectors.

Ikea Hackers shares this method for assembling the bed: One expedit unit is used horizontally as is while the other is cut down to form storage for the end of the bed. MDF is added on top of the two units and the 4x4 post is used in the corner without any storage to prop up that end of the MDF.

[Ikea Hackers]