My daughter fell in love with Signing Time, not that I should be recommending DVDs. She was a great signer by 12 months, though, and she could always match pitch with me!
We also have a piano, toy musical instruments, etc. All she wants is for me to play Celtic music or Twinkle Twinkle on the laptop. We have special lullaby music and Signing Time songs for in the car that she is soothed by (hates the car).