BYObed.  Here is how I built my bed.  It is a platform designed to
hold a queen-sized mattress.

I got some of the 2" angle-irons from Home Depot, used 4 of them
full-length (48"?) to make a subframe, like this:

===============
   ||    || ---   <-- L-iron on each corner
   ||    |||
   ||    |||
   ||    ||
   ||    ||
   ||    ||
===============

On top of that was some flat boards, attached together with flat
mending plates.  (You can't get a single board the right size,
60x80 for queen size.)

Around that are flat boards, 1x8s I think.

Holding the thing up are 4x4 posts.

Here's the overall plan:


===========================================    <-- 1x8s around outside
H --------------------------------------- H
H|                                       |H
H|     =============================  <----------- subframe (metal)
H|        [] H               H []        |H
H|           H               H           |H
H|           H               H           |H
H|           H               H           |H
H|           H               H           |H
H|           H               H           |H
H|           H               H           |H
H|           H               H           |H
H|        [] H               H [] <--------------- leg (post)
H|     =============================     |H
H|                                       |H
H --------------------------------------- H
===========================================



Around the edges are 1x8 (or 1x10 or 1x12, depending on how much
you want the mattress to stick out) pine boards, held together at
the corners, and attached to the flat board, by brackets
(L-shaped metal things).  These were attached basically in the
middle or a little below center, so that the frame and stuff
aren't visible from a side-view, like this:

||---------------------------------   <--- top edge of side board (1x8?)
||
||=================================   <--- flat board
||       HHHH XX     XX HHHH          <--- frame (metal)
||-------HHHH-----------HHHH-------  
         HHHH           HHHH        
         HHHH           HHHH          <--- legs (posts)

The legs are 4" square posts, made long enough so that I could
put plastic storage boxes and milk-crates under the bed.  (You
have to allow an extra couple of inches for the overhanging side
boards, don't forget.)  The trick for these is, how to attach
them to the rest of the bed?  The answer is, the tops of these
are in post mounting hardware made for porches.  The tops don't
fit exactly, so I had to trim them down a little.

Here is what the post mounting looks like (top view):
    ____
   |HHHH|
   |HHHH|     <--- screws in from the side to fasten to wood
  _|HHHH|_    <--- nuts & bolts hold it to the rest of the frame
===========   <--- frame (metal angle-irons)
  T      T    <--- nuts and ends of bolts

Of course, you make the flat main panels that you sleep on 80x60,
which is queen size.  I sawed these first, then put together and
attached the frame (metal pieces, held together by nice big
L-iron brackets and nuts & bolts with lockwashers).

Note: this is not the cheapest way to make a bed.  It winds up
costing like $80-100 because Home Depot is not the cheapest place
in the world.  They're nice because they'll saw things to the
right size for you on those awesome saws they have.  You have to
plan carefully to get the sizes right!  My newer bed that I built
out here was cheaper because I didn't use a metal subframe, I
used 2x4's instead, but it's also not quite as solid, and creaks
a little.

Also, you will want to have an electric screwdriver, to drive the
screws into all the wood pieces and the corner brackets that hold
everything together.  Otherwise you'll go crazy.

-Tom