Please identify these two kinds of Lego bricks (circa 1990's)
The first two are: 

Hinge Plate 2 x 4 with Articulated Joint - Male



Hinge Plate 2 x 4 with Articulated Joint - Female



They are still used in modern sets sometimes.



The last two are called "bracket" pieces. They have not appeared in any recent sets.

Bracket 2 x 3 - 1 x 3 (Train Signal Stand)



Bracket 2 x 2 - 1 x 4