Modern motherboards and CPUs underclock themselves automatically now. a 3.0 gig processor may only be running at 1.2gig for 99% of it's on time. Find some motherboard monitoring software and check it out for yourself
(See if your system is doing it)
As far as ram goes, I think the only way you can save power is to pull dimms out.
On some graphics cards, having a second monitor plugged in can take an additional 30-40% power. So if you have a second monitor but don't always need it, you can turn it off, that might save some power.