Perimeter of a rectangle-

http://www.funbrain.com/cgi-bin/poly.cgi?A1=s&A2=2&A15=1&INSTRUCTS=1

More rectangle perimeter-

http://www.aaamath.com/geo78-perimeter-rectangle.html

Perimeter of a square-

http://www.aaamath.com/geo78-perimeter-square.html