This is my very first published add-on. It still under development, but it already works!
Ledger keeps records of your income and expenses, like in a financial spreadsheet.
Download:
http://www.esoui.com/downloads/info1172-Ledger.html
GitHub:
https://github.com/haggen/Ledger
If you want in I'd love some company and help with:
1. Further development of the add-on code base
2. Financial concepts and formulas
3. Completion and translation of the interface texts
4. Testing and feedback of user experience
Any help is really appreciated, thanks a lot!