Abacus calculator. Calculating was never this easy. And it's Free Software now.
Contributing to Abacus
Abacus needs your help. You can write patches or just compile and use it and write bug reports. Ask for help on the mailing list or fork the code on github.
Code repository – http://github.com/pstuifzand/Abacus
Mailing list – http://groups.google.com/group/abacus-dev
Issue tracker – https://github.com/pstuifzand/Abacus/issues