I found this example of Hairy Skullcap on a wooded trail at O'Bannon State Park in Southern Indiana, on June 9, 2007. The first thing to catch my eye was the cluster of Snap Dragon-like flowers perched on a stem that was about 1 1/2 feet tall. The next thing was the fuzziness of the stem and leaves, which is fairly apparent in this photo. Also note the opposite, lightly toothed, and petioled (on a stem) leaves. According to Wildflowers of Mammoth Cave National Park, this should also have a square stem, though I don't remember noticing the shape of the stem at the time. The square stem is a characteristic of the Skullcap's being in the mint family.
According to Wildflowers of Mammoth Cave National Park, Different species of skullcap have been used to treat irritability and nervous conditions as well as insomnia and exaustion. I have found other sources online attributing these uses to skullcap species and adding on that it is also used as "anti-inflammatory, antispasmodic, slightly astringent, emmenagogue, febrifuge, nervine, sedative and strongly tonic" with a warning that an overdose can cause "giddiness, stupor, confusion and twitching". (http://altnature.com/gallery/skullcap.htm) I didn't, however, find any sources that attributed these uses to this specific species of skullcap.