What frequency/band lends itself to interstellar communication?
I actually think this would get more traction in the SciFi SE site. But with regards to what is currently being experimented with, check out the MESSENGER spacecraft. It holds the distance record for optical information transfer. That means lasers. As for frequency, they use infrared. I looked around but I couldn't find why infrared was used.

http://en.wikipedia.org/wiki/MESSENGER

http://en.wikipedia.org/wiki/Free-space_optical_communication