For specific ones: 
./Oracle12.1.0.2Events.txt
./Oracle12.1.0.1Events.txt 
./Oracle11.2.0.4Events.txt 
./Oracle11.2.0.1Events.txt 

Also see
../computer/OracleFuncCalls.html
for function - event mapping

General notes about events are below

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Ways to get events:

1. $ORACLE_HOME/rdbms/mesg/oraus.msg: documented (in the sense that simple text is provided)

2. http://yurichev.com/non-wiki-files/blog/events/11.2.0.1.0_linux86_events.txt
What's actually used in oracle binary. Probably collected from Mr. Yurichev's disassembly, e.g.
in file ktt.txt:
May call dbkdChkEventRdbmsErr (0x9CA4)
means there's event 40100 (related to tablespace), even though oraus.msg does not record it.
[Update 2016-02] See ../computer/OracleFuncCalls.html for instructions to extract all events
 
3. strings $ORACLE_HOME/bin/oracle > oracle.strings
vi oracle.strings
All events are around a certain location, such as 61% in vi for Oracle 9.2


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Events++ (or Event++)

New in 11gR1. Used to be in published document
Diagnostic Events in 10g and 11g [VIDEO] [ID 1402625.1]
But Oracle removed it later. (Most of its content is in a doc named "Events++".) 
This
How To Use The New 11g Events++ Syntax For Easier SQL Tracing Of Datapump Operations? (Doc ID 813737.1)
is still on MOS, and points out that | is replaced with comma in 12c.


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Errors in setting event and how to correct them.


***** minor error 214:

----------------------No level is needed
SQL> alter session set events = 'immediate trace name trace_buffer_on, level 4';
ERROR:
ORA-02194: event specification syntax error 230 (minor error 214) near ','

SQL> alter session set events = 'immediate trace name trace_buffer_on';

Session altered.


----------------------No comma is needed
SQL> alter session set events 'immediate trace name buffers, level 1';
ERROR:
ORA-02194: event specification syntax error 230 (minor error 214) near ','

SQL> alter session set events 'immediate trace name buffers level 1';

Session altered.


----------------------Missing level (from Steve Adams's book p.108)
SQL> alter session set events = 'immediate trace name heapdump_addr 80682060';
ERROR:
ORA-02194: event specification syntax error 230 (minor error 214) near '80682060'

SQL> alter session set events = 'immediate trace name heapdump_addr level 4, addr 80682060';

Session altered.


***** minor error 215:

----------------------Comma is needed
SQL> alter session set events '10046 trace name context forever level 12';
ERROR:
ORA-02194: event specification syntax error 230 (minor error 215) near 'LEVEL'

SQL> alter session set events '10046 trace name context forever, level 12';

Session altered.


***** minor error 286:

----------------------"Deadlock" is not a trace name, but an event name
SQL> alter session set events = '60 trace name deadlock';
ERROR:
ORA-02194: event specification syntax error 231 (minor error 286) near 'DEADLOCK'

SQL> alter session set events = 'deadlock trace name context';

Session altered.


----------------------Wrong spelling of trace name
SQL> alter session set events = 'immediate trace name row_cacheee level 12';
ERROR:
ORA-02194: event specification syntax error 231 (minor error 286) near 'ROW_CACHEEE'

SQL> alter session set events = 'immediate trace name row_cache level 12';

Session altered.


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How to find an event that was set in a session or system-wide?
(Ref: https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&doctype=HOWTO&id=436036.1)

In 8i through 10g:

To find in a session:
oradebug setorapid <v$process.pid>
oradebug dump events 1
(On UNIX/Linux, setorapid,setospid both work. But on Windows, in older versions, setorapid is
preferred in order to avoid hanging.)

To find events set system-wide:
oradebug setmypid
oradebug dump events 4

If you want to see what event was set in your current session, you can also 
exec dbms_system.read_ev

Event name, ID and level are recorded in the trace file.

In 11g and above:

To find in a session:
oradebug eventdump session

To find events set system-wide:
oradebug setmypid
oradebug eventdump system


Note that seeing the event correctly set does not mean what the event intends to modify in memory 
is guaranteed to have been set. For instance, setting event 10503 with alter session appears to 
have succeeded according to the above method. But the value of the PGA variable kxsusrgl the event 
attempts to change is changed only after instance bounce (to verify, run "oradebug dumpvar pga 
kxsusrgl").

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How to set multiple events on one line?

alter system set events '980 trace name errorstack forever: 942 trace name errorstatck forever';
----------------------or to dump bind variable runtime values
alter system set events '980 trace name errorstack level 3: 942 trace name errorstatck level 3';

You can only run that alter system once; subsequent errorstack events won't have any effect.
So putting them on one line is needed. To turn them off:

alter system set events '980 trace name errorstack off: 942 trace name errorstatck off';


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alter system set events versus dbms_system.set_ev

Using alter system to set an event sets events in the current instance. To set it in a specific session, 
oradebug setorapid... oradebug event..., or exec dbms_system.set_ev. When using dbms_system.set_ev, 
an empty 5th argument means trace name 'context':

exec dbms_system.set_ev(1234, 567, 10046, 12, '')
exec dbms_system.set_ev(1234, 567, 942, 3, 'errorstack')