Free Online VQF to OGG Converter

Audio format developed by the Nippon Telegraph and Telephone Corporation (NNT Labs); uses transform-domain weighted interleaved vector quantization to compress audio data; can be encoded in 80, 96, 112, 128, 160, and 192 kbps bitrates.

This format is free, which apparently is one of the reasons for its popularity. The used codecs supports variable bit rates (as a default), and .ogg files usually play back easily on all platforms. All things being equal, the sound quality exceeds that of mp3 somewhat.