The best investment teacher on the Web is, without a shred of doubt, The Big Picture. Go there today and read everything. Sample goodies.

For bond buyers; what matters most is not the return on your money, it's the return of your money.

Then there is this explanation of the current credit "problem:"

Start with a few million mortgages of varying credit-worthiness and create a series of residential mortgage-backed securities (RMBS) from them. Then take the RMBS and stratify them. Then leverage them up into collateral debt obligations (CDOs). Once that bundling is complete, make complex bets on which layers might default, via credit default swaps (CDS). Gee, how could anything possibly go wrong with that?!

Link to above article is here.