Dave Grohl covered many bands, and played many alternate versions of his songs.
There are also a lot of side projects like Probot.

Studio Covers

Baker Street (Gerry Rafferty)
Band On The Run (Wings)
Danny Says (Ramones)
Darling Nikki (Prince)
Down In The Park (Gary Numan)
Drive Me Wild (Vanity 6)
Gas Chamber (Angry Samoans)
Have A Cigar (Pink Floyd)
I'm In Love With A German Film Star (Passions)
Iron And Stone (The Obsessed)
Kiss The Bottle (Jawbreaker)
Life Of Illusion (Joe Walsh)
Ozone (Ace Frehly)
Requiem (Killing Joke)
Sister Europe (The Psychedelic Furs)