Spreadsheets 

net present value calculator. 

to find, with different probabilities, if a set of X values is statistically related to a set of Y values linearly and if so, find the relation. 

for finding the three degree curve that fits a set of points. 

for finding the four degree curve that fits a set of points. 

for finding the five degree curve that fits a set of points. 

for finding the exponential curve that fits a set of points. 

if you feed a set
of values, this sheet can tell you whether or not the values are "cooked" based on Benford's law.
For example entering all the numbers in an income tax return into the sheet can indicate if the return
is actual or created just to decieve the authorities. 

the Digital Camera Capability Index. 
Quadratic approximation is not available here because it can be more easily performed using HSB Grapher. It can also create graphs for quadratic approximation, the functions generated out of these higher degree approximation sheets and much more.
You can use OpenOffice to open and view all these sheets. I recommend Open Office Portable, which can be installed on USB drives and can be taken along anywhere  it does not need to be installed to host computers.
To save these spreadsheets, please do NOT rightclick to save target. Instead, click on the hyperlink, and the save dialog should open.