My Save the Date Cards arrived in the mail the other day, and I'm stoked!!
I spent HOURS googling cards for ideas and inspiration. Then, MORE time looking for a good price! I ended up using Vistaprint.com. They primarily work with businesses, but have great prices so I gave it a shot. I'm very pleased!
I simply picked one of our engagement photos. Photoshopped a banner with text across the front, and ordered the Oversized Postcards. They're 8.52 x 5.47, and I got the glossy 130 lb cardstock. I think they came to about $0.21 a piece! You can personalize your message on back and don't have the added expense of envelopes or regular stamps.