Listening to Powerslave right now as it's their only album whose album cover isn't off-puttingly grotesque. Interestingly, Bruce Dickinson has cited Peter Hammill as an influence on his singing, and I totally hear it, especially in the title track.

Also, the middle section of "Rime of the Ancient Mariner" sounds remarkably like late-period King Crimson - in particular, think "Elektrik" from The Power to Believe.