You're looking for the ones which java provides I take it? Here's a simple custom object:
String allOffsets = "";
TimeZone.getAvailableIDs().each()
{
TimeZone tz = TimeZone.getTimeZone(it);
allOffsets += tz.ID + " = " + tz.getOffset(System.currentTimeMillis()) + "\n";
}
allOffsets;
Notice that you need to provide the date so that the offset can be calculated properly.
Is that the sort of thing you're looking for?
(some results of the scripto)
Etc/GMT+12 = -43200000
Etc/GMT+11 = -39600000
Pacific/Midway = -39600000
Pacific/Niue = -39600000
Pacific/Pago_Pago = -39600000
Pacific/Samoa = -39600000
US/Samoa = -39600000
...
...