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