And to be quite frank with you, Yes.
Save the Dates can be anything you'd like. A formal letter explaining your wedding and where it is going to be, a magnet to hang on your dishwasher, a bookmark, a postcard, a formal card, really whatever you'd like it to be.
Basically the purpose behind the Save The Date is to do just that - make sure your friends and family mark their calendar for your wedding date - and whatever suits your personality is totally acceptable!
Now RSVP'ing via email to your wedding, well that's a whole nother story!
{the image is courtest of idovedesigns.com}