I recently had some discussions on PL/SQL coding standards centred around some documents I’d come across on the internet, as well as some internal company standards documents.
Steve Feuerstein has a useful page PL/SQL Standards linking to his own document and to two others:
Steven's Naming Conventions and Coding Standards, by Steve Feuerstein (12 page pdf).
PLSQL Standards Developed for the PLSQL Starter Framework-1.pdf, by Bill Coulam (34 page pdf).
Trivadis PL/SQL & SQL Coding Guidelines, by Roger Troller (50 page pdf).
Another interesting document is Naming and Coding Standards for SQL and PL/SQL by William Robertson (html), which emphasizes common sense in application of standards.
These are all valuable documents, but it was thought that many developers would not read and remain familiar with long documents of this kind, and a 2-page summary standards might be useful. Here is my attempt, as a Word document on Scribd: