Before you post:
* Try using the Search button to see if a similar question has already been answered
* Try reading the relevant parts of the Oracle documentation (see links below)
* Try performing a Google search

When you post:
* Give your post a meaningful title, so that people have some idea what it will be about. Titles like "Please help!" and "Newbie query" aren't very useful.
* Posts should contain OS name & version
* Posts should contain Oracle software version number to 4 decimal places
* Posts should contain cut & paste copies of actual inputs & output messages
* Use vb Code tags to make your post more readable. The most important of these is the code tag, which makes both code and examples clearer by using a proportional font and maintaining spacing - e.g. instead of this:

SQL> select *
2 from emp
3 where deptno = 10;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ----------- ---------- ---------- ----------
7782 CLARK MANAGER 7839 09-JUN-1981 2450 10
7934 MILLER CLERK 7782 23-JAN-1982 1300 10

...you get this:
Useful links:

Oracle Online Documentation:
Oracle 8.1.7
Oracle 9.2
Oracle 10.1
Oracle 11.2

Other Resources (thanks to Saravanan.R for many of these):
http://www.orafaq.com/
http://www.oracle-base.com/Index.php
http://www.ixora.com.au/q+a/index.html
http://www.llcsystems.com/FAQ.htm
http://www.arikaplan.com/oracle.html
http://www.csee.umbc.edu/help/
http://www.ss64.com/index.html
http://news.dcn-asu****/BOOKS/
An Introduction to Oracle SQL Statement Tuning (Bill Magee)
Introduction to Data Modelling (University of Texas)

Other forums:
Ask Tom
Quest PL/SQL Pipeline
comp.databases.oracle

Please feel free to suggest other tips and links; I will update this post from time to time.