FontLab vfb2ufo is a two-way command-line converter for Mac OS X and Windows. It’s available free of charge from FontLab.
vfb2ufo converts between development font formats: VFB and UFO (including the compressed variant UFOZ). It converts both ways: from VFB to UFO (or UFOZ) and from UFO (or UFOZ) to VFB. If you supply it with a VFB, it will output a UFO (or UFOZ if you use the -z option). If you supply it with a UFO or a UFOZ, it will output a VFB. It converts one VFB or UFO or UFOZ at a time, but you can write batch scripts to facilitate conversion of multiple files at once.