Oh my gosh - that is so funny.  And it made me remember something I had forgotten - I had done something similar to that.  I have two groups in my e-mail address book.  One is internal and represents all of the people in the various areas of the company for which I do ordering/budgetary work.  The other is entirely external and includes the members of a nationwide organization in which one of my bosses is involved.  Whenever I am planning time off, I always notify the internal group, so that everyone knows I am not there and can plan their ordering appropriately.  Well, of course, one day I type up this e-mail letting everyone know that I will be off on Monday, and I send it to the external group!  I realized my mistake almost immediately (why, oh why, isn't there a way to reclaim something after you've sent it?) and sent out an apology.  I did get a response from one person who said that he was glad my boss actually gives me time off and to enjoy my day!  It was quite embarrassing.