The Beatles - Rubber Soul: A transitional album. This was the beginning of their late Sixties peak period. Not perfect, but chock full of great songs.
The Rolling Stones - Beggars Banquet: My second favorite album of theirs after Sticky Fingers. Fluid record, with great tunes like Sympathy, Street Fighting Man, Parachute Woman and Stray Cat Blues. I like it even more than Let It Bleed.
The Velvet Underground and Nico - A grower. Well sequenced. It's only my second favorite because I instantly fell in love with the third album.
The Pixies - Doolittle: I agree with most of what Pugeye had to say about this. It has some really catchy songs (Here Comes Your Man, Monkey's Gone to Heaven), and I do think it's a pretty good CD. But I could just never get into this band. Probably their best, don't care about the rest (Trompe Le Monde sucked.)
The Beach Boys - Pet Sounds: Beautiful at times, but inconsistent song-wise.
Black Sabbath - Paranoid: This appealed to me in high school because my Metal band covered Paranoid. God I am sick of that song. Maybe overexposure is playing a small part here, but I could never listen to this again. The only songs on it I still like are Ferries Wear Boots and Hand of Doom. But it's still better than Master of Reality.
Van Morrisson - Astral Weeks: Don't understand the appeal of this. It reminds me of when I tried listening to Jackson Browne's Late for the Sky. What a snooze.