This is definitely a bug. A weird one actually. I too saw the same "No Actions Available" when I first clicked on that DataSources link. However, I then went around clicking some other links like "Web Applications (WAR)" under the Applications section and then came back to the DataSources link. And now I could see the "Add New Resource" button. Can you give it a try? If that works, let us know. We can file a JIRA.
I have the same problem, except that I never see the "Add New Resource" button. All I ever see is "No actions available" no matter where I click. I.e., Applications Summary tab, Datasources Summary tab, etc.
I get the same results with Firefox 3.5.15 and Google Chrome 10.0.648.205 running on Fedora 12. The server is running JBoss 6.0.0.Final on CentOS 5.5,
Note: I was editing my response to make it more accurate, and now the "Add a new resource" button shows up, sometimes...