Large sheet of reclaimed (actually used in Trafalgar Square to hold back the crowds at the Millennium New Year) 18mm ply, belt sanded it clean, routed the edges to bull-nosed...
Lots of 2x4 for support bolted to the wall with f*ck-off big bolts (as my builder would explain it to me ) with tenon joins (I think) for the frame.
More 2x4 as a leg (all 2x4 has routed edges)
Varnished a pale honey colour.

Holds multiple 19+20" monitors (CRT+LCD)
Solid as a rock - the wood is lovely and rich, knots and whirls abound from the ply - there's a nice 'line' where the ege of the ply is routed - nice!
Dirt cheap
Very satisfying