I’m often using the gdal library for reprojecting and resampling raster data but have rarely needed to do so with vector formats. When dealing with points, I usually sort out the conversion manually. For other vectors - polygons and polylines - often stored as shapefiles, the ogr library of tools can be quite useful. This page provides a handy overview with some example data available for download. Here is a more verbose description of dealing with projections of vectors.