US Locator Service: Returns coordinates for your address. Streets and Trips will do it and you can get the info from Google Maps.
Convert Degrees, Minutes and Seconds to Decimal equivalents.
Conversion info if you don't want to use the fcc site and'd rather do it yourself.
Deg-Min-Sec conversion to decimal degrees:
DD=Deg+(min/60)+(sec/3600)
So the longitude 122d35m18s is
122+(35/60)+(18/3600)
122+0.5833+0.005
122.5883 degrees
More help:
At the center, it's 0,0. As you move west, the longitudes are negative so if you live west of Greenwich (on the Prime Meridian), the Longitude you supply will be negative up to a maximum of -180. Same if you're east of Greenwich. Your numbers will be from 0 to 180.
From the equator, your latitudes will be positive, from 0 to 90 as you go north of the equator. The latitude will be negative as you go south of the equator, from 0 to -90.
This should help you when you're entering in your decimal numbers.