Yes, banks are closed today, in addition to the U.S. stock market, in celebration of Martin Luther King, Jr.'s birthday.
This means that most of us get a day off from work, a day away from the daily grind -- so we can slow-brew a cup of coffee, read over all of our favorite personal finance blogs, and figure out what we can do today, right now, to bring ourselves closer to financial freedom.
It also means most bill pay transactions, account transfers, and ACH deposits/withdrawals you have scheduled will not initiate until tomorrow.
"Bank holidays" are typically more than just your local branch getting closed for the holiday. It means the bank's transaction infrastructure is also on hold until the next open business day.
Of course, things like debit cards and credit cards continue functioning, or society would breakdown. But it's been my experience that MOST banks won't do much for you on a holiday.
One nice exception: ING Direct. Their transfers from an ING account to another ING account, or from an ING account to a Sharebuilder account (or vice versa!) occur instantly, regardless of whether the bank is open or closed for holiday.