If you are looking for a fast, easy way to find a latitude-longitude, visit the ESRI GIS Education Community's Latitude-Longitude Finder in the new Community Web Mapping Tools area.

This geocoder uses ArcGIS Online to find latitude-longitude from street addresses in the US, Canada, and most of Europe. It also includes world place names and multiple base maps. For those collecting data in the field, dragging the map while switching base maps between street, imagery, and topographic should allow you to obtain a reasonably precise location without a GPS.