FastCalc by Panayotis - FastCalc is a calculator optimized to minimize the distance the fingers have to move, in order to perform the basic calculator tasks.
For this reason only the 12 basic buttons of the mobile phone are used
Jasymca - Jasymca is a symbolic calculator. It solves and manipulates equations, handles basic calculus problems, and provides a few more typical functions of computer algebra systems. The syntax is loosely related to GNU-Maxima. While it is fun to play with mobile devices, it teaches the use of computer algebra systems, and may even be used to solve some real world problems
EasyCalcFree - A very simple calculator. Enter a list of up to 10 numbers, add labels.
Comes with hyper-intelligence: You can write *, x, /, div, divide, subtract, plus, minus, times, takeaway, or pls, tms, add...you will still get the same result
This calculator for java mobile phones can calculate binary, octal, decimal, hex numbers and convert it to each other. It supports logical expressions, parenthesisses, memory and 64bit integer arrithmetics. Operator precedence as in C++, C#, C, Java
Graphing Calculator - FREE app, designed to turn your cell phone into a Graphing Calculator.
It should work on all phones that support J2ME, like Nokia, Blackberry, Motorola, LG, Samsung, Sony Ericsson and more (specifically MIDP 2.0 and CLDC 1.1)