Here is a list of general or common aviation frequencies. Make sure to monitor these frequencies as you can often hear emergency radio traffic, pilots talking to each other, and other types of air communications.

Common/General Air Frequencies

121.5000 - VHF Guard (Emergency)
243.0000 - UHF Military Guard (Emergency)
122.9500 - Unicom/FBO
255.4000 - National Flight Service
123.0250 - Helicopter Air to Air
123.4500 - Pilot Air to Air
123.3000 - Pilot Air to Air
123.5000 - Pilot Air to Air
122.7500 - Pilot Air to Air