SHAPEFILE PROJECTIONFINDER is an approach in context with gis data and unknown projections. The target group of this program are mainly user who wants to integrate gis data without great effort in their projects and have no spezialised knowledge about coordinate systems.
You can see a video of the presentation in Salzburg and the following discussion in German HERE. With a click into the graphic (right) you get the FOSS4G poster presentation.
You can download a free version of this tool using registered EPSG-Codes of geotools 2.6.0.
IMPORTANT: It is possible to generate WKT (Well-Known-Text) for .prj-files using OGC or ESRI definitions .
Roberto Matellanes wrote a detailed Spanish description of Shapefile ProjectionFinder: http://www.gisandbeers.com/