The postal service has an interesting way of testing the delivery of first class mail. They get volunteers from all over the nation to agree to receive several pieces of mail each week and report what day they received it at www.reportez.com.
You can notify the USPS of your willingness to participate at the website, but it looks like they also send out query letters to people in areas where they want to test.
It appears they have another method of testing the mail, where they actually send you a handheld scanner and ask you to scan in the barcodes not only on the mail that they send, but the mail that you receive from other sources.
The process is all outsourced to IBM and the test envelopes are non-de script so no one at the local post office knows who is participating in the test.