Measurement

aaamath
http://aaamath.com/mea.html
 

Polygons

Math.com
http://math.com/school/subject3/lessons/S3U2L1GL.html

Area

Math.com
http://math.com/school/subject3/lessons/S3U2L4GL.html

Math Goodies
http://mathgoodies.com/lessons/vol1/area_rectangle.html

Surface area
formula http://math.com/tables/geometry/surfareas.htm