I recently had a home energy audit done by Masco (see www.wellhome.com). The process is fairly simple, and very educational. When you call for your audit, they will ask for a credit card and you pay for the audit. However, once the audit is complete, the cost is refunded by DTE, effectively making the audit free.
Even if the audit cost $100, for me it was well worth it. The technicians that came to my home were very professional and thorough. They went through my whole house to measure energy use and efficiency. They found a small gas leak in my basement that I had no idea was there. They measured the efficiency of my furnace and hot water heater. They were up in my attic taking pictures of insulation. They went around my entire house with an infrared device to find cold spots and places where extra insulation could help. All the while, they explained what they were doing and why. The last test is the blower-door test to measure the air-seal or "leakiness" of the house.
Two weeks later, the technician came back to my house with a full report on their findings and what measures were recommended to make my home more energy efficient. He also brought a proposal for the work proposed that included air sealing and extra insulation in my attic. At this time, DTE offers rebates for insulation that would take $700.00 off my total bill. Also, there is a tax credit on materials that would save an additional amount.
I have recommended Masco and the energy audit process to several friends and family members, and would encourage you to call too! Their number is 877-305-3011.