Heres the list, and comments, from the above site, which also contains reviews of Zep albums . . .
""Babe I'm Gonna Leave You" - A folk song by Anne Bredon, this was originally credited as "traditional, arranged by Jimmy Page," then "words and music by Jimmy Page," and then, following legal action, "Bredon/Page/Plant."
"Black Mountain Side" - uncredited version of a traditional folk tune previously recorded by Bert Jansch.
"Bring It On Home" - the first section is an uncredited cover of the Willie Dixon tune (as performed by the imposter Sonny Boy Williamson). Blogovich sez: This gets complicated in the imposter Sonny Boy part. There were indeed two of the dude, Rice Miller (the second Sonny Boy) and John Lee Williamson (Sonny Boy I) although Sonny Boy II wound up being, arguably, the more well-known, partly because he lasted longer Sonny Boy I was murdered at age 34 during a robbery, but we dont have time or space to get into all that; read a blues book if youre interested. Bottom line: Zep ripped the song off.
"Communication Breakdown" - apparently derived from Eddie Cochran's "Nervous Breakdown."
"Custard Pie" - uncredited cover of Bukka White's "Shake 'Em On Down," with lyrics from Sleepy John Estes's "Drop Down Daddy."
"Dazed And Confused" - uncredited cover of the Jake Holmes song (see The Above Ground Sound Of Jake Holmes). Blogovich sez: This is the one to which Jeff, who commented on the blog, refers.
"Hats Off To (Roy) Harper" - uncredited version of Bukka White's "Shake 'Em On Down."
"How Many More Times" - Part one is an uncredited cover of the Howlin' Wolf song (available on numerous compilations). Part two is an uncredited cover of Albert King's "The Hunter."
"In My Time Of Dying" - uncredited cover of the traditional song (as heard on Bob Dylan's debut).
"The Lemon Song" - uncredited cover of Howlin' Wolf's "Killing Floor" - Wolf's publisher sued Zeppelin in the early 70's and settled out of court.
"Moby Dick" - written and first recorded by Sleepy John Estes under the title "The Girl I Love," and later covered by Bobby Parker.
"Nobody's Fault But Mine" - uncredited cover of the Blind Willie Johnson blues.
"Since I've Been Lovin' You" - lyrics are the same as Moby Grape's "Never," though the music isn't similar.
"Stairway To Heaven" - the main guitar line is apparently from "Taurus" by Spirit. Blogovich sez: Not apparently. This one is startling. Taurus, by Spirit (great band, pick up a compilation at least, highly recommended), is an instrumental of three minutes' duration; Zep copied the entire song and used it as the intro to Stairway. Give it a listen. But sit down first. Ridiculous.
"White Summer" - uncredited cover of Davey Graham's "She Moved Through The Fair."
" Whole Lotta Love" - lyrics are from the Willie Dixon blues "You Need Love."
Heres one not from the site but from Blogovich: Give Sail Away by Deep Purple (1974 Burn album with David Coverdale on lead vocals) a listen and tell me Zeps Trampled Underfoot from Physical Graffiti (1975) isnt the same borrowed-from-Ritchie Blackmore riff, just speeded up. And Zep singer Robert Plant had the gall, at the height of the later Whitesnakes admittedly Zep-derivative success, to call Coverdale David Coverversion? Amazing arrogance and the pot calling the kettle black crap. Further, Plants got the gall to write forwards to blues books and such, while his band so overtly ripped off those same artists. Amazing arrogance, Percy.
Zep defenders say old blues artists did the same thing with tunes, borrowing, adjusting, and so on. And that is in some measure arguably true. But nobody ever did it to Zep's extent. Not even close. Perhaps they could have given just a wee bit of credit where it was due?
Thats why, despite the hours of enjoyment (and maybe thats enough for some people and thats OK) Zep provided, theyll always be a few cuts below the all-time greats in my estimation.