infraprint.com just started one about two weeks ago. I haven't had the opportunity to test it yet but it looks like it has all the features that you might need.
I'm planning to use them to print and mail custom letters through the USPS for a credit repair site I'm building.
For credit repair, you'll need to do certified mail for certain requests. This is something we're getting ready to launch :-) Feel free to reach out (info in profile), if we can help.
I'm planning to use them to print and mail custom letters through the USPS for a credit repair site I'm building.