osm2shape is yet another osm XML to shape file conversion utility. osm2shape.c is written in straight C and requires only libz, libexpat and libshape.
osm2shape.c can be fetched from the X-Plane scenery tools code base:
osm2shape lives in src/OneOffs/
As of this writing, osm2shape exports only ways as poly-lines. I am working on polygon export with support for multipolygons.
osm2shape.c is meant to be used in conjunction with osm_tile.c to first split the plane file, and then convert each 1x1 cell into a shape file for later use.