This year, conventional banks and other financial institutions are bad news for investors because of the sub-prime debacle.  By contrast, sharia-compliant instruments have been soaring. 

Funds operated by Amana, Azzad Asset Management, and Dow Jones Islamic Fund have all done very well indeed.  Amana Income Fund, for instance, has had a 13% rate of return so far this year, placing it among the top 2% of income funds. 

Sharia-compliant instruments are very conservative. Such instruments avoid firms that are heavily in debt, because investing in such firms would be seen as gambling, which is not permitted.  As well, because interest is haram, forbidden, conventional banks and other financial institutions are also ruled out.
In the long run, a basket of investments that is somewhat more aggressive produces better returns, but at this point in time risk-averse is the name of the game, and conventional banks and financial institutions are suffering big time.