Novel Concepts has developed and has patents pending for the world's thinnest forced convection (fan cooled) heat sink dubbed ThinSink... it's thinner than a credit card.
"ThinSink's 2400% improvement in volumetric cooling efficiency, includes fan and motor, and is achieved by rotating (via motor) a thin toroid (circular fan disc), which generates an axial to radial fluid flow field, and having the heat sink (credit card sized plate with aperture) parallel and within the radial portion of the flow field. The local radial velocity near the 40mm diameter rotating toroid's perimeter, at 6,000 rpm is ~12.6 m/s. This high velocity radial flow field enjoys further air volume (for addition cooling) due to entraining remote air (Bernoulli Effect). The volumetric cooling efficiency of today's leading overclocking heat sinks is ~0.0032 W/°C/cc, compared to 0.081 W/°C/cc for the credit card sized ThinSink."