Oh boy, do I ever have lots of suggestions! I guess these suggestions apply not only to Yahoo, but any company. Yahoo can lead the way by example, though.
a. More efficient coding means less servers needed to handle the growing http request load. Less servers = less infrastructure and routers and vips, etc. = less electricity used. (Added bonus: also means less $$ spent on hardware!) Set up an internal green coding council to publish internal guidelines for more efficient coding. Use smaller, more compact programming languages. Use threading in a compiled language like Java or C++ instead of the process model of interpretted languages like perl or PHP.
b. Only buy new hardware for server farms or development that has a "green" certification, like Energy-star compliant devices.
c. Encourage compression for disk storage, and especially for backup storage and log files. Less disk space needed = less disk drives to buy = less electricity to run the disks.
d. Heavily insulate all buildings/rooms that contain server farms. This will mean the air conditioning bill will go down. Put in a system that takes filtered outside air for the server room cooling instead of air conditioning if the outside temperature is colder than the air conditioning output. I've always wondered by companies have air conditioning in the server room in the middle of winter...
e. Put future server farms in more northerly locations where the temperature is cooler or more even in the first place. That means lower air conditioning and heating bills. Seattle? Chicago? Bangor? Canada? The bonus is that land is cheaper there too than Silicon Valley, as are employee salaries of people that might work there.
f. Encourage employees to use public transportation and carpooling. Subsidies for tokens, special carpool parking spots.
g. LCD displays instead of CRT displays for all Yahoo employees and server farms.
h. Encourage employees to use the stairs instead of the elevators.
i. Put LED lights in as many places as you can afford instead of incandescent or flourescent.
j. Put in motion detectors so that lights turn off when they are not in use. (Except in areas where they must always be on, by law.)
k. Pave future employee parking lots with bricks, cobblestones, or concrete. Lower manufacturing costs, and reduces dependence on tar and oil products.
l. If you have cafeterias in your buildings, reconfigure the HVAC so that you can reuse the heat from the ovens and stoves in the cafeterias for building heating in the winter time instead of just venting it to the outside. Of course, you need to put in a heat exchanger so that the cooking fumes, etc. do make their way into the buildings, only the heat.
m. Put in double-pane windows on all yahoo buildings. This reduces noise as well as keeping in the heat in or out (as appropriate for the season).
n. Designate some days as work-at-home days for those people that can work at home, and turn down the heating or cooling in the office (as appropriate) on those days. These days should also be designated "no regular meeting" days where only one-time or emergency meetings happen.
o. When making corporate buying decisions for tangible things like pens, light bulbs, office supplies, etc., factor in the cost of the packaging for those items. Prefer the items that are sold in bulk with less packaging, and especially avoid individually wrapped items.
p. Install awnings/shades for windows to reduce the amount of sunlight that hits the windows and that may enter in the buildings in the summer.
q. Encourage less face-to-face sales calls to reduce the energy used during travel. If sales calls or presentations can be done over the phone, or video, or webex, do so. If your sales organization is not segmented geographically, consider doing so to reduce the distances that sales reps need to travel in order to talk to their prospects.
2. Reuse and recycle
a. Set up some printers and/or copiers on each floor that have old paper in them already printed on one side. Instead of throwing out or shredding this used paper, put it back in into the trays of these "recycle printers" for printing stuff that is not so important. Only supply new growth (farmed wood) paper in the printer rooms.
b. Encourage coffee mugs at the coffee stations. Charge a small amount per paper cup, but you get coffee for free if you bring your own mug.
c. Encourage employees to use metal utensils and real plates in the cafeterias and lunch rooms, instead of disposables.
d. Make sure all old hardware is recycled. Old drives may be fine even if the laptop has died. For example, there may be ways to use the drives in cheap RAIDs, especially for non-production or offline machines.
e. When deciding which company to buy new servers and networking hardware from, factor in the energy cost of manufacturing that hardware. Also factor in the ease of recycling that hardware. Cars are now being designed to be more easily dismantled and recycled. Why not computer hardware?
f. Put collectors on the top of each building to passively collect and store rainwater in large tanks high up in the buildings. This water can be used for various gray-water (non-drinking water) purposes: the gravity fed water can be used as for emergency fire sprinkler systems even if the electricity supply or water pressure is lost. The water can also be used to flush toilets and urinals. It can be used in the sprinkler systems for the lawns, and in any decorative fountains there might be on your campuses, and even to fill any swimming pools if you have them in on-campus fitness centers. A reduction in the amount of water used from the local water utility will mean they have to use less energy to pump the water through the pipes to your offices. If the building is high enough, the water flowing down from the tank can be fed through a generator to generate a small amount of electricity that can be added to the corporate grid.
3. Use alternate energy
a. Cover the roofs of each Yahoo building with solar panels or solar water heating. Check out Nanosolar's printable solar panels (link below). They are not available yet, but they promise to be much cheaper than the traditional panels of today.
b. Fill the back-up generators with biodiesel instead of regular diesel. Better yet, look into being a tester for stationary fuel cells as backup generators instead. (link below)
c. Prefer green projects or companies when considering investments for the corporate reserves.
d. Set up some windmills on the Yahoo campuses. Put big Yahoo logos on them so you can use them as advertising. Also, rent them to the cell phone providers as a cell tower -- that way, someone else will pay for them.
e. Buy electricity from green energy providers.
f. If you have corporate shuttles, see if Yahoo can sign up as a demonstration site for fuel cell busses for those shuttles. See the link below for info on ISE Corporation's fuel cell busses.
g. When making corporate charitable donations, donate to replanting organizations and efforts. More plants = more CO2 captured from the atmosphere.
h. If you have cafeterias in your buildings, only buy food products from sustainable farming sources in order to encourage it.
i. If you have corporate security, and the security folks need vehicles, buy or lease hybrids or maybe even get into some fuel cell testing programs. Actually, that goes for any company-owned vehicles.
j. Hire an energy-czar to implement all my suggestions. ;-)
Well, there are lots more suggestions, but that's all I have time to write right now...