It's in fact 3 questions :
(made community wiki - not sure about the organisation, maybe the first answer should be edited to have the full ISO languages list?)
What about Wikipedia? Here is an explanation of the ISO 639 standard that lists short codes for language names and the Wikipedia list of languages has a good collection with language ISO codes in all kinds of formats.
I'm not sure ISO certifies programming languages.
As an institute it does issue standards for certain programming languages.
I assume you are referring to programming languages, not spoken or written languages.
ISO standardisation simply means that the language has gone through ISO's standardisation process. I don't know of any set of guidelines for programming languages in general.
ISO doesn't guarantee anything about the language beyond the claims it makes for itself. It's just a way to canonise, in a fairly definitive sense, what the language is. Of course, there are several beneficial outcomes, such as broad support by vendors, universities, governments, etc. But these tend to just happen. They're not guaranteed in any sense.
Also note David Thornley's comments to this answer for some insights into related standards bodies.