XML Namespace usage

Hi,
    I am trying to understand XML namespaces and its usage. The xml snippets which are present in the w3c doc is useful indeed, however I would appreciate if you can give me a couple of actual examples. If not could you point me in the right direction as to where I should look for examples?
    Thanks a lot
            Ravi Veeraraghav
            ravi@gemlogic.com