If you're not ready to make the switch to LED on your Christmas tree, consider using LED lights on a wreath you can use over and over each year. This idea is by Danny Seo, from his blog Simply Green. He says he used a grape vine wreath and went to town with a few strands of LED lights.
Make it even greener by using a recycled grape vine wreath from Napa Valley Grapevine Wreath Company!
Both the LED lights and wreath require a bit of investment, though the smaller the size, the less investment necessary. However, with only a little care, this will last for many years with only a little dusting between uses.