GeoFeeder is a simple and straightforward app for converting your geodata (mif/mid, shp, gml, kml, etc...) to GeoRSS. I downloaded the free trial and gave it a quick test on some basic files and it worked as advertised, including option to output ATOM/RSS and Simple/GML/W3C variants. On some larger/more complex files the app choked for me on loading the source file. Your mileage may vary, but its free to take a peek. The trial is limited to 30 days - after that you need to purchase a license for unlimited use. I don't think this is going to replace FME in anyone's' geotoolbox, but if you aren't already using Safe and have modest needs, Geofeedeer could be worth a look.