Magot is a cross-platform personal finance manager written in Python. A check-book like register GUI allows you to enter transactions and track bank accounts, incomes and expenses. It's based on formal accounting principles, PEAK and WxPython.
PyOrganizer is a cross-platform (Python/GTK) personal organizer, with a GUI optimized for the Nokia Internet Tablets (n810, n800, and n700). The financial/budgeting features are now operational, and rudimentary mileage tracking has just been added.