Love Supertramp.Crime of the Century by Supertramp
Insanity rocks!
Love Supertramp.
Queen II could also be considered a concept album. It's my fave of theirs and probably the "heaviest" album in my collection. It makes bands like Evanesence seem positively Britney Spears-ish by comparison.
The Alan Parsons Project has put out a few:
Pyramid (mysticism)
Turn of a Friendly Card (gambling)
I, Robot (technology)
Tales of Mystery and Imagination (Edgar Alan Poe themes)
Eye in the Sky (surveillance)
Vulture Culture (consumerism)