I second this. If you're gonna cite a concept album, go all the way-- its a really bizarre album but it works in its own weird way. Its also got a great variety of mood, textures, many memorable moments and quirky as hell!
I would also add Pink Floyd's Wish You Were Here (their best album IMO).
Dark Side of the Moon has some great moments, but overall I feel the album is a bit weak-- I really think its overrated (I say this as a Pink Floyd fan BTW). I would even prefer Animals to RABotM.
I see no mention of The Wall which is fine by me-- probably the poorest Pink Floyd album (there are some individual songs that are GREAT, but the album overall is bloated, confused, and way to self-important). There was a time where that was considered by many to be THE concept album. Ugh.
Sgt. Pepper's is good and Radiohead's OK Computer comes to mind, but I never *listen* to them as concept albums-- its just a good collection of songs.
~ josh