Easy hack or plugin for participating in the 1/18 SOPA strike?

As many of you know, there is a big “blackout” being organized to protest against the SOPA bill. I even see www.remarpro.com did a post about it. A lot of sites – Mozilla, Reddit, Twitpic, etc. – are going dark on 1/18. Rumor has it that even Twitter and Google might do it.

Anyway, I would like to black out my WP site as well and put up a message indicating why. Wondering if there’s an easy way to do this with a WP site (plugin?) The one way I’ve thought of so far is to upload a “.maintenance” file with the HTML in it, but I figured I’d ask you experts if there’s a smarter/better way.

Thanks.