Mathcad
Mathcad, by Mathsoft, is a fantastic tool for learning and using math on your computer. It's unique feature is that the math looks just like what you would write on paper, except it is "live." So if you change the value of a variable at the top of your page, it automatically calculates the resulting changes in the rest of your document. It does its calculations from left to right, top to bottom, following the order of operations of mathematics of course. One thing that you will see right away that is a little different is that when you define a variable in Mathcad, say x=5, it usually appears as x:=5. The extra colon is Mathcad's way of telling the program that you want to initially define something. Later on if you type x= Mathcad would automatically show you that x=5.

Mathsoft's Home Page
Mathsoft, the manufacturer of Mathcad, has a good web site that has a lot of information about Mathcad and mathematics. Click here to go the home page of Mathsoft.

Mathematica
Mathematica (by Wolfram Research) is the primary competitor to Mathsoft's "Mathcad." It didn't start out as nearly easy to use as Mathcad, but has come around (I think) to the "make it look as you would write it" maodel that Mathcad has used from the beginning. The Automatic Calculus and Algebra site uses Mathematica.