What is the minimum income you must earn to be required to file a 2007 individual federal income tax return as a single dependent?

I heard around $3,000.
Not knowing your income I would suggest you file out a 1040a if you have taxable income you may be eligible for the $300. rebate. You definitely should be eligible for Earned Income Credit. If you made very little you should get back what you have paid into taxes.
I made $903.00 paid $41.00 fed tax and $28.00 state tax. I am getting the $41. and the $28. back plus $71.00 Earned income credit. Since I am getting my taxes back I didn't qualify for the rebate.

Single dependents, you must file a return if any of the following apply.
• Your unearned income was more than $850.
• Your earned income was more than $5,350.
• Your gross income was more than the larger of:$850 (for 2008 $900), or Your earned income (up to $5,050) plus $300.
• Your self employed income is $400 or more.

Read: Your U.S. Tax Return: Filing Requirement for a Dependent (http://taxipay.blogspot.com/2008/02/filing-requirement-for-dependent.html)