The Case of the Serial Comma (txt) 
When you enumerate more than two things, you need a comma before the "or" or "and" (eg, the good, the bad, and the ugly). This is my rule of thumb for commas: if you would pause naturally when reading the sentence out aloud, that's where a comma should go. You pause between each item of a list, so it makes sense that a comma should go before an "or" or "and". Don't know why they taught me otherwise in primary school.
http://pages.swcp.com/info/essays/serial-comma.htm
When you enumerate more than two things, you need a comma before the "or" or "and" (eg, the good, the bad, and the ugly). This is my rule of thumb for commas: if you would pause naturally when reading the sentence out aloud, that's where a comma should go. You pause between each item of a list, so it makes sense that a comma should go before an "or" or "and". Don't know why they taught me otherwise in primary school.
http://pages.swcp.com/info/essays/serial-comma.htm
