Boards
There's a building site across the road from my office...
... with a lift that emits a high, piercing siren to signal it's climb/descent. It goes de-da-de-da-de-da-de-da every minute or so as someone else boards it. The result is that as I try to work Pulp's 'Your Sister's Clothes' is on permanent rotation in my head.
http://www.youtube.com/watch?v=Q91p1hKAqMU
What's on in your internal jukebox right now?