Below are two TI-Nspire documents from Spencer Williams that show visually the operations of adding and subtracting fractions. There is also a pdf file to support the use of these in the classroom. Thanks, Spencer, for sharing these.

Students will approximate the area under a curve using Riemann sums. This will be done by utilizing a program that computes the Riemann sum as well as drawing the graphical representation. The activity concludes with students discovering that if enough Riemann sums are used, then the area under a curve can be calculated with the required degree of precision.

http://education.ti.com/educationportal/activityexchange/Activity.do?cid...

From Sean Bird's website: "Put this [TI-Nspire] file in MyLib so that you can access the area approximation methods from any document."
The program will find the approximate areas for the left, right and midpt Reimann sums, as well as the trapezoid, Simpsons and numeric integral areas.
http://cs3.covenantchristian.org/bird/TTT/NspireCalc/area.tns

For other TI-Nspire files from Sean's website, visit:
http://cs3.covenantchristian.org/bird/Nspire.html

This is the first of three TI-Nspire documents on solving linear equations. This document introduces the concepts of true, false and open sentences, and the method of Guess-Check-Refine for solving linear equations.

Cups and Blobs with the TI-Nspire (see below) is an interactive introduction to the Balance Method of solving linear equations, which is then followed by Equation Solver with the TI-Nspire (see below).

All that is missing is a TI-Nspire document that demonstrates the Backtracking Method for solving Linear Equations. Any takers :-) ?

This TI-Nspire document by John Hanna introduces the new Program Editor in TI-Nspire v1.3 released January 2008. It covers an overview, basic programming concepts, and some stuff for 'experts'.
http://www.johnhanna.us/nspire/tns_files/Programming_TI-Nspire_1.3.tns

Students have a choice of two ways to use this document: students specify the steps of the process and the CAS follows these instructions ("student as spectator") OR students actually enter each line (either literally or in terms of some action upon the previous line (e.g. eq2 + (b/2a)^2) and the CAS engine verifies that this line agrees algebraically with the previous line (high student involvement). Dynamic algebra in the hands of the students!
http://compasstech.com.au/TNSINTRO/TI-NspireCD/mystuff/Dynamic_Algebra_S...

Three possible models present themselves: two substitution methods and one elimination. The first and last allow equations to be entered in any form.

The second requires these to be entered in "y =" form - but they can be entered from either spreadsheet or graph.
http://compasstech.com.au/TNSINTRO/TI-NspireCD/mystuff/Dynamic_Algebra_S...

A key challenge of using computer algebra with students in the early years of secondary school lies in not allowing the tool to do all the work!

In this TI-Nspire document, a student enters the equation to be solved in cell B2, and then enters each step of the solution in the cells below. As each step is entered, the "check" column indicates whether this is correct or incorrect. The final result may be checked against the graph on the next page.
http://compasstech.com.au/TNSINTRO/TI-NspireCD/mystuff/CAS_Eqns/Equation...

Type in your function and this clever TI-Nspire program will find the derivative and show all of the setting out. Marvellous!

Riemann Sums 1
Define the function f(1). Then use trap(b,a,n) to find the area under the function between a and b with n divisions using the trapezoidal rule. The function lrs(b,a,n) uses the lefthand rule, rrs(b,a,n) uses the righthand rule and sr(b,a,n) uses Simpson's Rule. How cool is that!