I's assume "Echoes" would be the best song to get high to, though keep in mind I'm brand-new to pot, and my only try so far (back in January), yielded no high at all, so I wouldn't know for sure.
I'd also assume that the worst song to listen to while high would be "Careful with that Axe, Eugene."
I have recently become a huge Floyd fan. Can explain it, really... but their music is like nobody else's. They were just... something different. Something amazing.