You can't because the regulators dont release their soundness assessments to the public. And anyone that thinks a big bank can't blow out might want to take at look at Bank of New England or whatever that monster in Chicago was years ago - Continental Illinois or whatever it was. Commercial loans pop a lot of them.
There are a number of firms that officially rate banks for safety. Weiss, Veribanc, AM Best, Bauer, and others. To get the info you will have to cough up the $3K+ subscription fee or use your local library to obtain access however. In terms of FDIC; some good sources for how the account insurance coverage works can be found at these links: Insurance is per depositor per account. The FDIC summary is here: http://www.fdic.gov/deposit/deposits/insured/ownership3.html A summary by ING Direct is here: http://home.ingdirect.com/faqs/faqs.asp?s=FDIC#limits A summary by Emigrant Direct is here: https://www.emigrantdirect.com/EmigrantDirectWeb/documents/EDFDICInfo.pdf - Greg B.
like i said before, put your money into money market funds. they operate transparently. you know what they invest in, and you know the financial soundness of those investments. the same cannot be said for your bank. there have been far, far more bank failures than cases where a mmf drops below $1 nav.
I have found that a hole in the ground in the safest place to hold money. As long as the earth exists you are guaranteed the money.