Peter Roosen wrote a very nice interactive GPS software tool to help us choose a GPS receiver. Unfortunately it is in German, so we made a brief recapitulation in English. The program, NAVIG2, and the translation can be found here.
Falke Bruinsma’s website maps.innersource.com allows you to upload GPS track logs and overlay those tracks onto aerial photos and topographic maps. A number of GPS track formats are supported including a simple latitude/longitude comma separated file, Garmin MapSource text file and Delorme Map’n’Go & Street Atlas (GPL).
GPSVisualizer is an on-line tool that creates SVG (Scalable Vector Graphics) maps and profiles from GPS waypoints and tracks. GPS Visualizer supports uploaded GPX track and waypoint files, OziExplorer track and waypoint files, Geocaching.com LOC files, IGC log files, Garmin Forerunner Logbook XML files, tab-delimited or comma-separated text files, Cetus GPS and PathAway .pdb files, and NetStumbler log files. You can also enter waypoint data manually, if you just need to plot a few points. The output from GPS Visualizer can be viewed in any Web browser -- assuming you have installed Adobe's free SVG Viewer plug-in -- or edited in a graphics application such as Adobe Illustrator.
GPS2CAD.com GPS software is making freely available an extremely valuable "coordinate conversion" web page to websites and webmasters that serve the GIS - GPS - CAD industries. This page, hosted on the GPS2CAD website, is created as a "web application" and converts between more than 40 world-wide grid and datum projections. For example, your users can enter Latitude and Longitude from the popular WGS-84 format used by GPS devices, and convert them to a UTM or State Plane coordinate system. It is custom built and uses the coordinate conversion tools from Franson.com (another extremely popular conversion toolkit).
NewSatNav is an online application that helps you to choose your best (car) satellite navigator, according to your chosen criteria. The site is still very young, but will bring more results in the near future.