To learn a lot more about cosmic rays, check out the Cosmic and Heliospheric Learning Center 's page on cosmic rays . I think that the description given on our cosmic ray page and the pages linked from it are what you want. If you've got a more specific question, feel free to send more email.
Cosmic rays are particles - the nuclei of elements in the periodic table.
They have nothing to do with the cosmic microwave background. Please visit the COBE home page for more on the cosmic background. I worry from your question that you don't really understand what cosmic rays are. Cosmic rays are sub-atomic particles that are moving at a good fraction of the speed of light. The velocity of cosmic rays can go from a small fraction of the speed of light up to about .999999999999 times the speed of light.