Yesterday, Intel released the PowerTOP utility. It allows to monitor closely the power consumption and to diagnose what software is using the most power.

It requires (at least) a 2.6.21 kernel with /proc/timer_stat (enabled through CONFIG_TIMER_STATS, [commit]).

I've just made this tool available in Mandriva Cooker, in the powertop package. I'm afraid it will unearth some very bad habits from net_applet... (will try as soon as we have a 2.6.21 kernel ready for Cooker)