I would make sure you have some governmental insurance. Due to the uncertainty of the current credit environment, you don't want to be left holding the bag if the bank you chose fails. Even some of the big ones are suspect right now. Check out this article.
http://www.bloomberg.com/apps/news?p...d=aEUtlgwzL_qc
What this means is that you either need to open up 10 different accounts for $100k each or buy some kind of supplemental insurance from the bank that you want to use.
One good option might be to open a trading account at a place like Etrade where the bank is connected to the trading account. You invest 500k into a super short term bond fund or similar, and receive SIPC protection up to 500k. Then sweep the interest payments/dividends into your Etrade high yield savings account which is FDIC insured up to 100k. That covers 600k and gives you ATM access to 100k of it through local Etrade ATMs. If you need more than 100k, just sell some of the bond funds that day.
I am not sure of another brokerage that does this, but I am sure one exists. In this way you would be fully gov't insured and fairly liquid with only two accounts.