I use a spreadsheet to do my record-keeping. I have multiple sheets that do: cash flow, the balance sheet, income and expenditure (double entry), and profit & loss. Everything's linked together nicely: e.g., if you make a new transaction in the income sheet, it will be reflected everywhere else. Insanely simple. No need to use MYOB etc. Can copy the data out and paste into Matlab, Mathematica etc.

Message me if you want a copy of the template.