Reading Wilson and Alroy's Record Reviews, I found out about the band Spirit.
They were mentioned as having written the song that Led Zeppelin ripped off to come up with the intro for Stairway to Heaven. The Spirit song was Taurus, and the guitar part is played about 40 seconds into the song.
Other direct influences from Spirit: Aerosmith's Somebody has a guitar/vocal solo very similar to the one on Spirit's Uncle Jack.
Listening to Spirit's album The Twelve Dreams of Doctor Sardonicus, I came across the song When I Touch You, and was pretty impressed with it.