Installing LED lights is #1 on my list these days because it is simple, cheap, and something that just about everyone can do by themselves. LEDs (light emitting diodes) are much more energy efficient than incandescent bulbs AND they are much safer than CFLs (compact flourscent lights) because flourescent light fixtures all contain mercury which means they have to be treated as "hazardous materials" and disposed of properly (you can't just throw them away with your normal trash - they need to be taken to a recycler that specializes in flourscent bulbs).
And because many home buyers will contact the utility companies to see how much emergy the home usually uses before they purchase the home. In other words, that is part of their decision making process, so the lower you can get your utility bills in the year before you sell, the better.
Do as much as you can comfortably afford to do and don't forget to check with your city, county, and state governments to see if they have any grant money or low-interest loan programs that you can take advantage of.
Neighborhood Revitalizaiton Program: Minneapolis
http://www.nrp.org/r2/aboutnrp/FAQ.html Neighborhood Revitalization Program: Minneapolis
Minneapolis City Living:
Hennepin County Grants & Funding
As far as the big repairs or improvements that buyers like to see are:
* New windows and frames
* High efficiency furnaces & air conditioners
* Tankless water heaters
* Energy star appliances
* Retractable awnings
* Corn burning fireplace inserts or stoves
* Radiant floor heat.
One note of caution though, choose your materials and contractors wisely. I suggest using organizations like Minnesota Green Star Certification, Angie's List, Checkbook.org, Consumer's Guide, or Consumer's Reports to help you find materials that perform well and a reputable contractor. And remember, just because a company spends a lot of money on advertising and everyone knows their name, that doesn't necessarily mean they are the best. In fact, there is a window manufacturer that has a very good reputation (because they advertise a lot), but everyone I talk to regrets having purchased their windows.
Check out Minnesota Green Star Certification webpage: http://www.mngreenstar.org/ for more information.
I've been suggesting several green ideas to improve a homes marketability. Some are relatively easy and inexpensive.
Two ideas can dramatically reduce a home's heating and cooling cost - first, seal window and door air leaks. Second, install a programmable thermostat.
A third idea would be to upgrade to energy efficient appliances.
Do you have other suggestions? I would like to hear about them.