I've enjoyed the quality and versatility of Moo cards. I first wrote about them here, last September. In brief, Moo is a "print on demand" service. From the Moo website you can bring in your photos from Flickr, Facebook or your own computer and receive high quality, inexpensive cards back very quickly.
In May I ordered and used a two hundred for a national conference. My wife did the layout of three different pictures from Kosovo, each representing a different theme. On the back we had printed a number of prayer requests for each theme. We handed out these beautiful little cards (28 mm x70 mm) as reminders to friends and acquaintances.
Moo just added post cards to their line-up too. I regularly use post cards as thank you notes and reminders. They're much cheaper to mail than a regular card, and include a picture of the country in which I live. The downside is that the local post card pictures are usually very lame. I might just order a batch of Moo Post Cards from my own Flickr feed!
via Download Squad