Via Greg Mankiw, here's a useful interactive guide to the subprime mortgage mess.

And in honor of Paul Krugman's horrifying-yet-too-convincing column (in which he reminds us all that it is easier to make a tightly constructed argument for doom if you don't spend all your time ranting about the evils of GWB or Barack Obama), here's an excerpt from my favorite personal-finance book, Andrew Tobias' The Only Investment Guide You'll Ever Need. Tobias has a chapter about miscellaneous investment topics, and here (quote may be slightly off) is his definition of a margin call:

A margin call is what alerts you to the fact that your life is going to hell and that you never should have gotten into the market when you did, let alone on margin.