Deductions & credits

For most simple returns, you can file for free if you get in early enough.  Turbotax has "free" online for simple federal returns, and the state return is also free if you file during the "Absolute zero" promotion (assuming they offer it again.)After Absolute Zero ends, a simple federal return may be free but the state can be up to $39.  

Even if you have a complicated return, you can file for free using the Tax Freedom version if your income is less than around $33,000 (the threshold may change for this year.)  It's a separate web site, though.  https://turbotax.intuit.com/taxfreedom/  

All the flavors of Turbotax online aren't available yet, usually early December.

If you have a situation that requires you to upgrade to the Deluxe version (such as, you have a form that is not included in the free version and your income is too high for Tax Freedom version) then the cheapest way to file is to buy Turbotax as a CD or download from a third party retailer like Costco, Amazon, Target or Staples to install on your own computer.  Make sure you get the "Federal + E-file + State" version so you get 1 free state.  Also be aware that state e-filing will cost $25 on top of the price for the CD or download, but you can print and mail your state return for no additional charge.