Senator Johanns and Senator Nelson, both NE
Congressman Fortenberry, also NE

I used the forms on their respective websites. I also sent one directly to Senator Johanns email as it was indicated as an option at the bottom of the form.

And for whatever it's worth, I did the form on the White House website. I tried to find a form for Michelle Obama, but couldn't locate it.

Looking at some of these responses, it's somewhat disheartening to hear what the senators/congressmen are saying.