I learned bookkeeping on Khan Academy with the two types of accounting: accrual basis and cash accounting. Assets, liabilities and equity words entered my head, currently busy with some Khan brain teasers.
And I managed to solve all currently published exercises on Khan Academy (129/129) :-) Kudos to my TI-89 which helped me out so many times! However, the unknown and legendary Black Hole badges aren't yet in my journeyer backpack... And to earn them, it is currently impossible because... the answer is ... hidden in Kahn's source code. Check badges/point_badges.py and exercise_completion_count_badges.py to unveil the secret...
Fabian Bellard's scientific web calculator is very powerful! I discovered it today while reading an advogato entry on him!
