Essentially, the FDIC insures deposits in several "ownership categories," which means you may actually be insured beyond the $100,000 limit you most often hear about. For example, single accounts in your name are covered up to $100,000 per bank. Joint accounts are a separate category and also get their own $100,000 of coverage per person per bank.
So if you and your wife have a joint savings account with $300,000 in it, $200,000 of that account is insured. Retirement accounts - which must be an actual retirement account, such as a IRA, SEP, etc., not just an account you consider part of your retirement savings - are covered for up to $250,000.
These limits apply only to bank deposits.