Here are a list of free iPad Apps that may be useful in teaching. The first column gives the App. name, the second the developer (and version) and the last column the topics covered by the App.

Arithmetic

Name of App.

Basic Fraction

Digital Abacus

Get Primes!

Interactive Times Table

Long Division Touch

Rounding Whole Numbers

Times Table+

Developer (v)

Explorer Technologies (1.53)

ExactLead (2.4)

The App Tower Inc. (1.4)

Fall Day Software Inc. (1.0.1)

Regular Berry Software LLC (1.1.1)

King's Apps (1.0)

Vladimir Grinman (3.0)

Useful for

Fraction Operations

Place Value, Addition and Subtraction

Times Tables, Division

Long Division

Determining and Finding Primes

Rounding Whole Numbers

Times Tables, Division

Algebra

Name of App.

Complex Number Cruncher

iFactor Quadratics

Factor Polynomials

Developer (v)

Neil Woodcock  (1.0)

iStuff (1.1)

Reddolution (2.1)

Useful for

Basic Operators, Modulus and Argument

Factorising Quadratics

Factorising and Solving up to Octics 

Geometry

Name of App.

Areas ?

CalcThagoras

Circle Geometry

Geoboard

Triangle Solver

Developer (v)

Gakko Net Inc (2.9)

Marlon Trotzinski (2.0)

Hup Hup Apps (1.0)

Clarity Innovations (2.1)

William Jockusch  (5.3)

Useful for

Areas of Shapes

Rectangle, Triangle and Circle Perimeter and Area

Tangents, Angles in Circles

Perimeter, Area, Angles, Congruence and Fractions

Sine, Cosine Rules and Triangle Area

Calculus

Name of App.

Calculus: Areas and Volumes

Developer (v)

Planlet Systems Inc. (1.01)

Useful for

Areas and Volumes between Curves

Fractions, Percentages and Decimals

Name of App.

Basic Fraction

PercentDiff

Developer (v)

Explorer Technologies (1.52)

Shaolo LLC (2.61)

Useful for

Fraction Operations

Percentage of a Number Increase/Decrease etc.

Statistics and Probability

Name of App.

Pie Chart 3D Free

Developer (v)

ORPI.pl (1.0)

Useful for

Drawing Pie Charts

Calculators

Name of App.

Calculator ∞ 

Quadratic Formula Solver 

Developer (v)

An Truong (3.9.7)

Ryan Ashcraft (3.1.1)

Useful for

Almost Everything !

Solves Quadratics (Real and Complex Answers)

Graphing

Name of App.

Desmos Graphing Calculator

Quick Graph: Your Scientific Graphing Calculator

Developer (v)

Desmos, Inc.  (2.0.1)

Alex Restrepo (2.6.2)

Useful for

Graphing Functions

2D and 3D Graphing