Software I can use to get help in physics

Does anyone know any software I can use to get help in physics, math, and circuits. I need to use these along with my text books.

 

When you say tools, what do you mean. Are they tools for doing math fuctions like:
diff(x^2+2,x) or are they educational. WHen you enter a fuction in Mathematica, like one to differentiate an equation, does it just pop out the answer, or does it show the steps. I remeber seeing a website that shows steps when you enter and equation. I think they were using web Mathematica.

Wow, that website you gave has a plethora of data. Thanks.

I already have a CAS on my TI-89.

 

WHich one is better. Maple 10 or Mathematica 5.2?