Aside from saving paper, online tax filing makes it easier to organize all of your tax information and keeps an online record of your tax history. Online tax filing services may inform you of deductions and benefits you weren't aware you qualified for. You're also less likely to make a mistake when filing online, as tax filing programs will alert you if you've left something important out.
Of course, if you think you may benefit from in-person advice, you may want to consult with a tax preparer.
IRS Free File is one service for online filing. Taxpayers who earn less than $57,000 per year can use the service for free to file federal returns. A number of other tax prep services, like TurboTax, TaxACT and H&R Block, offer online filing.