J.G.
We used Knott Insulation to put in our attic insulation and HIGHLY recommend them! They were HONEST and very nice to work with. We've noticed a huge difference in our bills both in summer and winter with the new insulation. If we had read more about it before, we probably would have done the radiant barrier also.
We've also found that using a window air conditioner helps. It's just like a boost to the central unit, but it helps to suck out the moisture. Then your central isn't having to run as much to keep the house cool and dry. We've actually done it for years, but then read recently how it helps with energy costs.
Recently we've been opening up the windows at night and keeping them open for a little while in the morning. Then we close up the house to keep the cooler air in. Our central isn't having to cut on until much later this way, if at all.
We've cut our electric bills (we're all electric, no natural gas at all) from 1/3-1/2, depending on month and conditions.