I ordered mine from Vistaprint. They were mailed out the same day. My fiance and I created our own then uploaded the picture to Vistaprint and it was super simple. I also wanted preaddressed envelopes, but I had a very difficult finding a website that would provide preaddressed envelopes for save the date magnets so I ordered preaddressed envelopes separately from Basic Invite.
Re: Save the Dates
P.S. Vistaprint is having great sales right now!