Amendment 27 was added in 1992, Raedwulf, which was the last addition. I think that last actual change of an earlier provision was in 1971, was Amendment 26 set the voting age at 18 for all states.

In 1972, the ERA passed congress but failed 3 states shy of ratification. I was reintroduced to Congress in 1982, but no progress has been made as far as I know.

Numerous changes were made to the Constitution in the 20th century. Changes are slow and difficult, but by now means is it a stagnant document.

http://memory.loc.gov/const/amend.html