Usava esta aplicação para converter de e para GPX, mas tem muito mais potencial:
GPS Visualizer is a free, easy-to-use online utility that creates maps and profiles from GPS data (tracks and waypoints, including GPX files), street addresses, or simple coordinates. Use it to see where you've been, plan where you're going, or visualize geographic data (business locations, scientific observations, events, customers, real estate, geotagged photos, "GPS drawing," etc.).
GPS Visualizer can read data files from many different sources, including but not limited to: GPX (a standard format used with many devices and programs, including Garmin's eTrex, GPSMAP, Oregon, Dakota, Colorado, & Nüvi series), Google Earth (.kml/.kmz), Geocaching.com (.loc), FAI/IGC glider logs, MS Excel, Google Spreadsheets, XML feeds, Garmin Forerunner (.xml/.hst/.tcx), Timex Trainer, OziExplorer, Cetus GPS, PathAway, cotoGPS, CompeGPS, TomTom (.pgl), IGN Rando (.rdn), Emtac Trine, Suunto X9/X9i (.sdf), Fugawi, NetStumbler, and of course tab-delimited or comma-separated text.
FizzyCalc - Programa para converter coordenadas (freeware)
FizzyCalc - Conversor de vários tipos de Coordenadas