This one is a bit of an oldie, but a {really, really} goodie.  These fabulously fun yet simple invitations are from the May 2005 wedding of Robin Rosenthal and Matt Hall featured in the Winter 2006 edition of Martha Stewart Weddings:

{I love the text bubble on the rsvp card}

The invitations themselves are so wonderfully creative, but then there are all of the wedding details:

{mustaches as wedding props}

Robin is an amazing graphic designer and illustrator, working as Deputy Art Director at Martha Stewart Kids magazine until March 2006.  Check out her full portfolio here!

{top two images via Robin Rosenthal, bottom two via Black Eiffel}