Compound interest basics

Interest is the basis of modern capital markets. Depending on whether you are lending or borrowing, it can be viewed as a return on an asset (lending) or the cost of capital (borrowing). This tutorial gives an introduction to this fundamental concept, including what it means to compound. It also gives a rule of thumb that might make it easy to do some rough interest calculations in your head.
Introduction to compound interest
Introduction to compound interest
The rule of 72 for compound interest
Using the Rule of 72 to approximate how long it will take for an investment to double at a given interest rate

Interest basics

This is a good introduction to the basic concept of interest. We will warn you that it is an older video so Sal's sound and handwriting weren't quite up to snuff then.
Introduction to interest
What interest is. Simple versus compound interest.
Interest (part 2)
More on simple and compound interest

Credit cards and loans

Most of us have borrowed to buy something. Credit cards, in particular, can be quite convenient (but dangerous if not used in moderation). This tutorial explains credit card interest, how credit card companies make money and a far more silly way of borrowing money called "payday" loans.
Annual percentage rate (APR) and effective APR
The difference between APR and effective APR
Institutional roles in issuing and processing credit cards
The institutions involved in processing your credit credit and how they relate to each other
Payday loans
How Payday lending works

Continuous compound interest and e

This is an older tutorial (notice the low-res, bad handwriting) about one of the coolest numbers in reality and how it falls out of our innate desire to compound interest continuously.
e and compound interest
Sal introduces a very special number in the world of math (and beyond!), the constant e.
e as a limit
Sal continues the discussion on e, this time digging deeper into the mathematical definition of e.
Formula for continuously compounding interest

Personal bankruptcy

Back in the day (like medieval Europe), you would actually be thrown in jail if you couldn't pay your debts (debtor's prison). That seemed like a pretty awful thing to do (not to mention that lenders are much less likely to be paid by someone rotting in prison), so governments created an "out" called bankruptcy (which, as you'll see, is a pseudo-painful "reset" button on your finances).
Personal bankruptcy: Chapters 7 and 13
Chapter 7 and Chapter 13 personal bankruptcy.