In the first example the correct solution is with the comma:
I work at Google, the search company.
The reason: The comma in this case denotes a non-defining relative clause. Google is a well-known company, therefore you do not need to define which Google you mean; there's only one! Therefore, if the following works:
I work at Google.
Then you can use a comma to create a non-defining relative clause to comment on the first sentence.
As for the second example - this is a bit different. In lists you usually do not put a comma before and, but this sometimes results in ambiguity, like for example:
These cables are red, yellow, black and white.
This sentence is ambiguous as the last item in the list, "black and white" might be considered as one item; a cable with two colors!
To help disambiguate such cases there's something we call a serial comma. You can put it before "and" preceding the last item in a list, especially for the aforementioned reasons. The result would be:
These cables are red, yellow, black, and white.