This is my v2 of a presentation on ideas for going beyond the Application Express default graphs and info on 3 popular Javascript graphing libraries that can be incorporated into Apex Applications.
I came across this PL/SQL page today which has pointers to a lot of interesting stuff you can do with PL/SQL.
From the page:
"This library is a collection of various utility packages for PL/SQL, as well as links to useful libraries hosted and maintained elsewhere."