Just caught sight of this on the AVR website... They've announced a new "picoPower" line of AVR microcontrollers.
Apparently it is a subfamily of AVR's will be released that offer significantly reduced power draw, both in Active and Sleeping modes. Active power saving schemes will apparently include both allowing more control over shutting peripheral clocks down (we've already seen that) and new ideas, such as shutting down the Flash for any periods of time within a given instruction cycle where the fetch is already completed.
One interesting claim is that a new "sleeping BOD" will allow the BOD to be automatically disabled during deep sleep modes, shaving 20 uA off the nominal power-down power consumption without compromising system integrity, brown-out detection response times, etc.
Another claim is that an AVR using picoPower technology will be able to drive 32 kHz RTC crystal in Power-Save mode resulting in total consumption (with a sleeping BOD) of 650 nA.
Planned devices will be drawn from the current ATmega family, with a P suffix after their names: