Below is an interesting article about how deeply religious Muslim investors avoided the full brunt of the stock market crash:
Hint: if you can't invest in companies that charge interest on loans, you avoid investing in banks.
Update: my friend, M. Izak, reminds us that Muslims aren't against banks per se. He says the current banking system is anti-Islamic because it charges interest rather than fees. Banks may rely on fees instead of interest payments but have chosen to rely on interest payments.