I use the DreamCoder to test and to build PL/SQL, execute anonymous blocks. It is this way easy to develop and test the code PL/SQL . There are other products in the market ( PL/SQL Developer , TOAD) , but they are but complicated of using.
More information :
DreamCoder for Oracle
http://www.mentattech.com
PL/SQL Developer
www.allroundautomations.nl
TOAD
www.quest.com
Regards,
Pete