Jeffrey Friedl has done a bunch of great plugins/piglets for Lightroom. This plugin – for Lightroom 2.0 and later – allows you to geoencode your photos from within Lightroom. This means you can put your GPS data right into your META information of your photos.
If you don’t have a GPS unit or a tracklog, you can specify locations by pinpointing them in Yahoo! Maps or Google Maps, then cut-n-pasting the url. You can also specify a GeoHash, or a latitude/longitude pair in one of a variety of formats, such as:
35.011065, 135.782201 35° 0' 39.83" N, 135° 46' 55.92" E 35 0 40, 135 46 56
Check out Jeffrey’s “GPS-Support” Geoencoding Plugin for Lightroom
Introduction and Instructions for the plugin can be found here.