What is the difference between Ubuntu Ready and Certified

Ubuntu Ready is a test performed by the manufacturer of the system and reviewed by Canonical. Because of that, Canonical can not ensure that the system will remain working with any stable or security updates released for that Ubuntu version, after the date of the test.

Ubuntu Ready has now been discontinued and will have no new listings beyond 11.04
http://blog.canonical.com/2011/07/18/ubuntu-certification-is-changing/

Ubuntu Certified is based on tests done by Canonical on hardware that we have in our labs. Canonical will continue to test that the system works correctly with updates released for that Ubuntu version. Canonical will also test the system with releases under development to ensure no regressions are introduced. This testing will continue until the next available LTS.

In summary, Ubuntu Ready tells you that the system works with an specific build of Ubuntu. Ubuntu Certified is an ongoing effort to maintaining a system working for an specific release and future upgrades.