Can a dependent file own tax return if claimed on parents' tax return?

Yes. The IRS has income guidelines for determining whether dependents are required to file tax returns. Generally, for 2008 income, dependents are required to file if single under 65 with earned income of over $5,450 ($5,700 for 2009) or if married under 65 with earned income of over $6,800 ($7,100 for 2008). Even if your income is below the level requiring you to file, you should file if income tax was withheld from your earnings in order to receive a refund of that tax.