Ask Harry Reid about his strong immigration bill from 1993
Calling "flip-flop" isn't as effective as discussing actual policies. So, if you want to do a public service, ask Reid about that bill at one of his public appearances and then upload video of his response to video sharing sites; see the question authority page for an action plan.
For instance, you can ask Reid a question like the following:
"Sen. Reid, your 1993 immigration bill - something you later apologized for - sought to, among many other things, reduce alien smuggling. If you'd pursued that bill instead of withdrawing it, wouldn't there be fewer alien smuggling cases than there have been?"
I can come up with better questions on request, but based on over three years' experience I'm not going to get my hopes up. However, if you're in Nevada and want to do a public service, ask him that question or leave your information in comments and I'll come up with something more iron-clad.