Automatically Retrieving Album Names for Unknown Album Songs in iTunes
Tagalicious

Whilst it has been discontinued, Tagalicious has worked well for me for a long time, finding accurate results to missing info on music in my iTunes library.

MusicBrainz Picard

A cross-platform ID3 tag finder for songs. Despite the fact that it doesn't integrate with iTunes specifically, the ID3 tags can be read by iTunes.