I have a smal red patch the size of a 1/2 dollar on my scalp, right above where a widows peak would be. What could it be, and how should I treat it?

Red Patch. What you describe may be a simple fungal infection of the skin, but it also could be more serious, such as a basal cell cancer. Your age and sun exposure are important information to help your physician treat the area, or biopsy the area to get an accurate diagnosis, to help plan with treatment.
More characteristics. Is it itchy? Scaly? Lumpy? Uniform in redness? Has it appeared gradually or all at once? What's your age? Do you have eczema or seborrhea? Do you have a pet? Have you recently changed shampoo? All these items are necessary data to help in diagnosis of the patch. See your doctor for proper assessment, having the answers to these questions handy.