Will multiple accounts at the same bank, like having both a checking and savings account, increase my coverage limits?
Depends. It’s how the account ownership is titled that matters. If it is an individual account, then you get $100,000 per individual at that bank, no matter how many different accounts you open up. To get more coverage, you could open up an account at another bank. However, if you open up a joint account with someone else that can increase your limits.

How much FDIC coverage can a couple get at one bank?
If structured properly, a couple such as a husband and wife can shield up to $400,000 at one single bank without involving legal trust vehicles. In addition to the $100,000 per individual account, if two people open a joint account then each will have up $100,000 in coverage ($200,000 total for the account) [Source]. If you throw in revocable trust accounts, a couple can theoretically shield up to $600,000 at one institution:

Are business bank accounts covered by FDIC insurance?
Yes, but you have to be careful. Since legally there is no difference between a sole proprietorship and an individual, one cannot gain more coverage at a single bank by opening a “business” account when you are a sole proprietorship. The business account would still fall under the $100,000 individual cap. However, in the case of partnerships, corporations, and LLCs, because these are separate legal entities, they do get a separate $100,000 per entity.

Where would you put $1,000,000 in cash if you had to? Spread across 10 banks (or more to cover accrued interest)?
First of all, there are very few scenarios where I’d want $1,000,000 sitting around in cash. I’d probably choose to take more risk with it. But I really don’t think I’d bother with 10+ banks. Most likely, I would place it in a retail money market fund at a reputable firm, like the Vanguard Prime Money Market Fund. That way, even if Vanguard goes bankrupt, this will not affect the underlying conservative investments. A retail money market fund has never “broken the buck”. Alternatively, I would buy traditional US Treasury Bonds or TIPS either directly or through a Treasury money market fund.

What about the Certificate of Deposit Account Registry Service (CDARS)?
Another way to increase FDIC insurance are services like that of CDARS.com. Essentially, they spread your large deposits into $100k chunks across a network of banks, but without any effort on your part. From their website:

According to this Bankrate article, due to the added costs of this system CDARS rates are usually about 0.15% lower than the “normal” CDs from the network banks. Also, the network banks seem to be smaller local banks, which may not offer the most aggressive rates in the first place.

Am I worried about my money at Washington Mutual?
Not really. WaMu is much better financially than IndyMac was. But again, due to the realities of fractional-reserve banking, if people panic and start pulling out tons of money from WaMu, then they can still fail due to liquidity issues. I am not going to be one of those people. If it fails, it fails. Most banks on the FDIC “problem list” do not fail. I have faith in the FDIC process, and I still have much less than $100,000 in my accounts. Finally, I never keep all my funds in any one bank. I can still run my day-to-day cashflow needs from other banks.