I have made a simple 3d city for a project I am working on. I was thinking about makeing a night scene but I want a simple way to add windows to the buildings. the buildings are just simple boxes and cylinders. Right now I just have a simple bump map on them to make it look like they have detail on them. I was thinking that maybe I could just make some sort of texture map that had glowing squares representing windows but I dont know...any good suggestions?

Yep, that'd be the way. Use a Grayscale map and apply it to the Glow Channel in the shader tree. If the squares are too bright, Multiply a Value Shader in with the glow channel and slide the shader around until you get a glow that looks right.

I've also used a nested shader with a marble or noise element to vary the brightness between windows (and even in the individual windows) to indicate shadows behind the curtains. Helps sell an image.

Ok I'll give it a try this weekend and let you know what happened.