If you may be claimed as a dependent by somebody else, then you are required to file if your income exceeds your available standard deduction which for 2005 is the greater of $800 or your earned income plus $250 (i.e. up to a maximum of $5,250).
If you have no taxable income you do not need to file. If your taxable income is below the indicated amounts above and you had income tax withheld, you should consider filing in order to receive a refund of your withheld income tax.
I recommend you consider filing a return if you had federal or state income tax withheld.
Because it is impossible for me to identify and consider ALL the relevant facts, this advice is not intended or written to be used for the purpose of avoiding penalties, and cannot be used for that purpose.