I need to know how to calculate the square foot of a building, or
room, that is oddly shaped.  I need to know how to take the shape, and
place it in a larger shape, ie. rectangle, square...and then subtract
the odd shape section from the whole.

If you have a floor plan you can cut it out and weigh it on a
sensitive balance. then cut out a square of known area and weigh it.
From the twoo measurements you can calculate the area of the
odd-shaped piece

HI,
Mikewa-ga's suggestion is a possibility.  The heavier the paper or
cardboard is that you can use the more accurate the result will be.

Most oddly shaped rooms  - if the walls are straight - can be defined
as one or two rectangles and a few triangles.  You may be right that
it is easier to place the plan on rectangle than encloses the area and
subtract the areas not covered by the plan.
If you do not have a plan of the room(s) with the lengths of the
walls, you are going to have to measure them, ...
But before I go on, it would help greatly if you could describe what
information you do have and a rough description of the shape of the
room.
For example:  it has one right-angle (90°) corner, the corners at the
ends of those walls are greater than 90°s, these walls extend to meet
a fifth wall that is (or is not) parallel with one of the first two
walls.
OR:  The room is basically two rectangles but the one and/or other
wall (which one/s?) are at greater than 90° from (which wall/s).

Of course, a picture is worth 1000 words. Here is a suggestion from
another question:
"If you're not using a photoposting site, http://www.photobucket.com is a
good place to use. I look forward to your clarification."

Okay?  Looking forward to helping, Myaorin

Go here and purchase the tool to measure the odd shaped space.

http://www.measurearea.com/

Disclaimer: I have no financial interest in this company yadda yadda yadda.

There is an easy way to do this mathematically if all the walls are
straight. You just need the coordinates of all the corners:

http://astronomy.swin.edu.au/~pbourke/geometry/polyarea/

Well, you cannot make any assumptions about linearity of the edges of
the shape and the angles. Even if you cut the odd shape out a larger
rectangle, you will still have another odd shaped cutout to deal with.

In that case, something like the quadtree method might do the trick:

Basically you start by drawing a bounding rectangle the shape that fit
it snugly. This is level 0. Then divide the rectangle along the
centerlines into four smaller rectangles of equal area. This is level
1.

If any rectangle contains a portion of the boundary, then divide it
into smaller rectangles. (Level 2)

Repeat the process recursively for each rectangle until you reach a
point where the small rectangles enclose a tiny chunk of the boundary
and you can reasonably estimate the fraction of the area inside and
outside the boundary.

Then the areas of all the rectangles inside the shape + the fractional
areas will give you the net area.

This is a discrete method and hence carries some amount of error. But
it will work for all 2-D shapes and you can improve accuracy by
splitting the rectangles some more. It also means a lot of work
keeping track of the rectangles!

Another physical solution on the lines of the balance method is to
flood the room with a known quantity of water (reasonably large
amount) and measure the height of the water level reached. Then the
area is known directly, provided there are no leakages.

This problem must have many different solutions, but I tell how I
would do it personally. first you need a white cardboard where you
place a center point with a straight, symmetrical cross. You place the
cardboard in approximately middle of the room. Then you need a
measuring tape that reaches to every corner of the room. Then you need
to measure distance to each corner and direction in degrees of an
angle. Placing the cardboard so that lines of the cross point to
points of the compass makes measuring of the angle easier. For example
N=0 E=90. You can use thin string and a protractor to determine angle
more accurately. Place another end of the string to the center and
another to the corner and straighten it by tightening. If there is
round walls you need to measure string of the arc too. Then you have
two options to calculate the plane. Traditional way would be to use
trigonometry, which is a field of it's own. Another and easier way
would be to place center point and coordinates of the corners to a
program like autocad, combine corners and make computer to calculate
the floor.
P.S. 
I wouldn't recommend filling room with water because it easily makes mildew to grow.

Scsorr78,
If you are still around, the above commment reminded me that there is
a formula for finding the area of a triangle based on the lengths of
it sides.

Find a point in the room that allows you to define trangles from it to
the corners and intruding points of the room.  With the measurements,
you can calculate and add together the areas of the triangles.

http://www.mste.uiuc.edu/dildine/heron/triarea.html