GpsPrune is an application for viewing, editing and converting
coordinate data from GPS systems. Basically it's a tool to let you
play with your GPS data after you get home from your trip.

It can load data from arbitrary text-based formats (for example,
any tab-separated or comma-separated file) or Xml, or directly from
a GPS receiver. It can display the data (as map view using openstreetmap
images and as altitude profile), edit this data (for example delete
points and ranges, sort waypoints, compress tracks), and save the
data (in various text-based formats). It can also export data as a
Gpx file, or as Kml/Kmz for import into Google Earth, or send it
to a GPS receiver.

WWW: http://activityworkshop.net/software/gpsprune/