Another table that is useful is:
SELECT * FROM user_objects WHERE object_type='TRIGGER';
You can also use this to query views, indexes etc etc
Check out ALL_TRIGGERS:
http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/statviews_2107.htm#i1592586
Use the Oracle documentation and search for keyword "trigger" in your browser.
This approach should work with other metadata type questions.
Source: Stackoverflow.com