I'm working on an iOS Postcard app, so I tried them out. lob.com is a really great service, very easy to set up and get started. Do note that in my test it took

I'm working on an iOS Postcard app, so I tried them out. lob.com is a really great service, very easy to set up and get started. Do note that in my test it took over ten business days from ordering the card to deliver, so it is good for marketing postcards, but not good for transactional postcards (e.g., welcome to the service type things).