Osmium now includes OGR support. OGR is a popular Open Source library for converting different GIS storage formats into each other. It supports PostGIS, Shapefiles, Spatialite, and many other formats. I had started working on OGR integration many weeks ago, but didn’t quite finish it. I have now added the last bit: Support for OGR Multipolygons. This opens up a lot of new possibilities for Osmium users.