Other than the one I linked to, "Lullaby of London" (and perhaps also "Rainy Night in Soho") by the Pogues is a good one. "Night Vision" by Suzanne Vega has a certain lullaby-ish quality to it. Kinda. And it's a very good song.

I also have a stubborn fondness for Tobira no Mukou he by Yellow Generation, although it's not as lullaby-ish as I Will by Sowelu, which...isn't all that lullaby-ish itself. But it's very, very pretty, especially if you like sweet, mournful jpop.