OK Computer, by Radiohead (1997): If there is one mainstream album that I remember starting to get described using the "p-word," this is it. It's sort of a concept album (though about what I have no idea), certainly works best as a whole, and has the band working in a lot of different sonic areas. There were comparisons to Pink Floyd, as I recall. It's even got an "epic," depending on your point of view ("Paranoid Android" is a whole 6.5 minutes long!). Is it really prog? Not to my ears. Does it matter? Not a bit. It's mostly brilliant - almost worth the price of admission alone for the Melotron drenched "Exit Music (For a Film)" - and was my gateway drug for Radiohead.