If your AGI is less than $52k and you are under 50 years old, you can do federal for free (including efiling)at a number of sites (I used H & R block's
http://www.hrblock.com/taxes/partner/index.jsp?otpPartnerId=180).
I guess I just outed myself as being young and less than wealthy.
I did have to pay for state filing, but you can just do the federal for free (my state refund was just enough to pay for the filing fee, and I was feeling lazy) and then do the state by hand.
I agree with the above comments, certified mail doesn't prove you actually mailed your taxes, it just proves you mailed
something and seems like a waste.