Didn't use any money in the Dependent Care Flex Spending Acct, can I deduct it on Form 2441 line 24? And, on what form and line do I put the credit?

No - the amounts you report on Form 2441 are the amounts actually paid to the care provider. If you didn't use up all of your flex spending account for tax year 2010, you lose it. Remember, this money was deducted from your pay pre-tax, so you can't expect to get a credit or deduction on money that was never taxed in the first place