This site is particularly interested in human structures (communications towers, tall buildings, etc.) that kill nocturnal migrants. One particularly hot area right now is wind power. People are struggling to determine how many birds are killed by turbines, and how those numbers can be lowered.
Here is an interesting link (that I have not previously seen) containing quite a bit of information on the subject:
While I'm not sure I agree with everything on that site, there is a lot of interesting information.