Whole Lotta Love - Well there is no denying that some of the lyrics are staright stolen from Willie Dixon's "You Need Loving", most famously recorded by Muddy Waters. Additionally the very last part of the song Robert sings "..shake for me girl, I wanna be your backdoor man", which are staright off another Willie song "Back Door Man". The Small Faces recorded the song in 1966, and that is the version that Plant really liked, but imo, the music is not very close at all. You be the judge. Here's Muddy's version as well as the Small Faces version:
The Lemon Song - Another that is slightly muddled. The first 1:30 is, lyrically, a definite rip-off of Howlin' Wolf's "Killing Floor". But the remainder of the song is unique, as well as the music throughout the whole song.
Moby Dick - The guitar riff to this song is definitely similar to Bobby Parker's "Watch Your Step". I can concede this point, especially considering Jimmy's penchant for stealing songs. However, this is primarily a showpiece for John Bonham on the drums, which has absolutely nothing to do with anyone other than Bonzo himself.
Bring it on Home - The first 1:40 of this song is pure theft of, yet another, Willie Dixon song. It was made famous by Sonny Boy Williamson II, and there can be no mistaking LZ stole the first 1:40, but from that point on there is nothing similar at all. So basically, 1/3 of this song you can put in the rip off column, 2/3 pure Led Zeppelin at their ass kicking finest.