I have a Canon 40D with the 17-85 IS lens. Something tells me that this will be fine for any daytime pictures I would like to take. However I am wanting to get some good nighttime shots of the buildings. I plan to bring/borrow a tripod for nighttime stability. What would be a good lens to borrow or steal? Ok, maybe not steal, but I may rent a lens for the day. <BR> <BR>Thanks!

You can always get some great cityscape shots with a wide angle, like a 10-20 or 12-24. Anything in that range should produce some great shots.