How can I increase the value of my home?

We bought a new house in 2007. The house was not complete (we purchased from the builder during a financial crunch). When completing the house, we installed all hardwood floors, slate flooring in baths, custom kitchen cabinets, granite countertops. However, what we could not change was the square footage. There is really no way to increase that. We have now landscaped the yard and added sod. What else can help increase the value of a home? When we had it appraised, the appraiser only went by comp home sales. Is this done by sq ft only? We love the size of our home. But we also love doing projects around the house that will increase its value. Can anyone make suggestions?