Read only, best of Oracle security, locating passwords and UKOUG
A couple of quick links; Tanel had a great post recently titled Oracle Security, Part 2: Your read only accounts aren’t that read only that discusses the issue of read only tables.
Alex posted last week two presentations; the first is "Best of Oracle Security 2007", which is in German and the second is "Retrieving Sensitive Information from Oracle Databases" which is in English.