Radio Shack Cat # 33-4050
http://www.radioshack.com/category.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F007%5F002%5F014%5F000&Page=1&find=sound%20meter(keyword)&hp=search
or the more expensive digital version.
Get a Stereophile test cd2, or the better yet, the Rives test cd. Read the room acoustics basics on rives.com on how to measure the listening room(including the adjustment factor chart for the rat shack meter).
You basically play test tone cd, while reading volumes at the listening chair w/the meter. Each track has a different frequency recorded at the same volume. Chart your results on the graph you can print off rives.com.
What most rooms do is make the bass region way too loud at certain frequencies, vs. how it would be ideally. Speaker placement and room treatments address the problem. It's much easier than it sounds, and will probably shock you at how much your room affects your sound. Cheers,
Spencer