It can get complicated depending on the type of investments, but some of the best known broker dealers, like Goldman Sachs, Morgan Stanley, Lehman Brothers and even Bear Stearns and Wachovia also have what's referred to as excess SIPC (also known as CAPCO Or Customer Asset Protection) which insures assets above the SIPC insurance. So if you have more than $500,000 at one of the 15 participating institutions you will be protected for the assets or value of those assets above that amount.You can find out more information at www.sipc.com or www.capcoexcess.com.
It always pays to do your homework. You should put your money with an FDIC insured bank or a SIPC insured broker dealer and preferably one who purchases that excess SIPC. But you should do your homework on the financial institution that you are investing with. It doesn't mean that bigger is necessarily better. Just make sure your money is in the hands of a financial institution that is weathering the storm better than others.