These are a few of my favourite slow songs that I could come up with at the top of my head:

Mogwai-<i>Stanley Kubrick.</i>
Björk-<i>Possibly Maybe.</i>
Brian Eno-<i>Spider and I.</i>
Zero 7-<i>In Time.</i>
The Sugarcubes-<i>Birthday.</i>
Death Cab for Cutie-<i>A Lack of Colour.</i>

I have a lot more, but the list would be very long. Yeah, I'm a sucker for slow songs. :P