Heard the argument that since much of what the federal government does these days - Freddie Mac, Social Security, Medicare, you name it - is not within explicitly listed Enumerated Powers in the Constitution, all these programs, as long as they are federal, are unconstitutional. Any truth to it?
-- EDIT --
In the comments there arose a question on the subject of what it means for something to be unconstitutional. Some argue that something is not unconstitutional as long as the courts haven't ruled it is.
Assuming so, in a hypothetical case where someone challenged the aforementioned social programs on the grounds they weren't explicitly given in the Enumerated Powers, what could the courts point to in the Constitution to defend them?
Is it the general welfare clause as mentioned by RWW in the first answer? Could it be something other than the general welfare clause? Are there any specific cases?