One of Led Zeppelin's biggest hits is "Stairway to Heaven" which starts with a meandering guitar line in a minor scale and then gets heavier with some interesting lyrics.
Another cool song is D'yer Maker which has a common interval pattern and has cool vocals and all around a catchy tune.
"Immigrant Song" is another hit of Led Zeppelin, all around rocking with great bass drumgs and electric guitar. The vocals are also pretty cool.
Really great you can find concerts on youtube and really get to experience this music as it was played.
"Kashmir" is another cool song of theirs that has an intense guitar riff and intricate vocals.
"Black Dog" is another rocking song. Zeppelin is all around a very rocking band!! I will have to research if its about a dog or what someday maybe.
"Whole Lotta Love" is another hit of theirs that like all their songs you can frequently catch on radio stations today.
Though the song that follows is probably my favorite. I also really like "Over The Hills and Far Away" it takes a while to get rocking but the foreplay makes it great.
One of my favorite Zeppelin songs is "Tangerine" which is a love song it has cool instrumentals and interesting vocals.