Bit-Tech saw a very small 120W PSU at CES 2006 in Las Vegas.
It's the MiniBox picoPSU. This power supply is designed for embedded systems and it's barely the size of an ATX connector and has a couple of Molex connectors and a floppy connector.
It's designed for use in embedded systems where space is at a premium. It's 100% silent, has a lack of messy cables and provides enough power to keep a Pentium M or Via C3 processor juiced up, depending on the other peripherals in the system.
Just imagine the modding possibilities when your power supply is no bigger than a couple of AA batteries!