The "Business of Software" blog (I'm not affiliated in any way) is giving away a program called "DoNotDisturb" for free. He bought rights to give the program away for several months from the author, which I found interesting.
They also have a free ebook for downloading.
You have to (as far as I can tell) fill in an information form.
There's a very tiny link at the bottom of the registration form for the ebook, if you want to get both in one go. I've downloaded but not yet tried the program.
http://blog.business.../do-not-disturb.html 
