RoadMap is a navigation program for Unix and PocketPC that displays street maps. Most of the maps are provided by the US Census Bureau, and thus only the US has a decent coverage at this time. A specific area can be displayed by entering a street address (street number, street name, city, and state). It interfaces with a GPS receiver through gpsd or the serial line to track the car position. It has been designed to be usable on a Linux desktop or laptop computer, or on a PDA (Linux or PocketPC).
gvSIG is an easy to use Java desktop GIS. It has a friendly interface, and can access some popular formats (e.g. SHP, DGN, DXF, DWG, TIFF, JPEG, ECW, SID, etc). It will integrate in a single view both local vector and raster data, as well as remote data through WMS or WCS. It allows layout design for printing. It is meant for end-users of geographical information, and currently has Spanish, Valencian, English, and 6 more interfaces. It's designed to be easily extended.
Mapnik is a toolkit for developing GIS applications. At the core is a C++ shared library providing algorithms/patterns for spatial data access and visualization. Essentially a collection of geographic objects (map, layer, datasource, feature, and geometry), the library doesn't rely on "windowing systems" and can be deployed in any server environment. It is intended to play fair in a multi-threaded environment and is aimed primarily, but not exclusively, at Web-based development. High-level Python bindings (boost.python) facilitate rapid application development, targeting zope3, django, etc.
mapview is an application for viewing maps on Palm OS handhelds. You can scroll through a map and switch between different layers. Layers may be used for different zoom levels. mapview includes a Perl program for building maps from image files on a Unix/Linux desktop. Instructions and a Makefile for building a demo map are included.
Roadnav is an in-car navigation system capable of running on a variety of operating systems, including Linux, Windows, and Mac OS X. It can obtain a car's present location from a GPS unit, plot street maps of the area, and provide verbal turn by turn directions to any location in the USA. It uses the free TIGER/Line files from the US Census Bureau to build the maps, along with the GNIS state and topical gazetteer data from the USGS to identify locations.