Take a Humorous Approach - Funny Save the Dates
Whichever save the date style you use for your announcements, you can still have a little fun with the wording if you want to. You would probably not extend this approach to a more formal wedding, but you can still add something a little different to make it stick in people's minds.
There are many save the date ideas out there you could use, but even if you go for the standard postcard, you can incorporate some funny save the date wording. Take this design with cupcakes on it, for example. Instead of the standard Save the Date heading, you might go for "Save the Date For Eating Some Cake."
There's a save the date template on the Zazzle website, that is worded "We Are Doin' It on [Date]. Save the Date!" Not for everyone, but is certainly humorous.
Film buffs may like to take a leaf from Clint Eastwood's book, with a save the date heading "Go Ahead Punks, Make Our Day."
For an extremely casual and funny approach to word your save the date, why not try this idea (right). A series of pictures tells the story of the groom-to-be passing out on a night out, with the save the date wording written on his face. The main wording on the save the date says "Don't Let Our Wedding, Pass You Out By!"
Of course this approach won't suit many weddings, but does give a great idea of what you are to expect if you attend the wedding. Whichever way you word your save the date, make it personal to you.