Nero has a "Normalise Audio" function when burning audio CD's but I must admit I've never looked for the option when burning an MP3 disc....

SoundForge has a batch processing option which can normalise audio files in bulk.

You could look upon MidiPlayer as a "bulk normaliser" although I'd still check the levels afterwards. I assume it works by analysing note volumes, expression settings and channel levels to get some idea of absolute level; with the best will in the workld this will not be absolutely accurate for a specific keyboard (although it does a pretty good job for me!).

Midiplay is invaluable for me; my PSR3000 is very sensitive to levels in Midi Files in that setting channel levels too high results in audible clipping of the audio waveform (especially the drum track).