Free Graphing Calculator from Microsoft: Mathematics Calculator

If you are a college student (and many high schools) you have access to https://www.dreamspark.com.  If you are a college student or someone with an email account with <dot>EDU (or .EDU) you can get all of the software at https://www.dreamspark.com.

I have always been a big calculator nut, I used a TI-59 when I was in college, it had a magnetic strip that would store programs, and I had the printer so it was useful, when it worked.  There were a lot of RPN calculators around, my manager Joe Shirey, just told me about his 25 year old HP-15c that still works (my caution Joe, is to make sure to check those batteries!).  Joe’s revealing that he had a 25 year old calculator was quite a surprise as I didn’t think he was all that old, certainly isn’t very cynical.

This is an awesome calculator, and the price is right for students: Free through Dreamspark.