FreeTaxUSA. I've used it for six or seven years, and as it says, it's free. It's online, no need to download software. My return is not too complex but it does involve MFS status, dividends/capital gains and itemized deductions. They have been spot-on accurate. I used to double-check them by doing a 1040 on my own (I used to work for H&R Block and was an IRS volunteer for 20 years so I am very familiar with tax prep) but I don't bother with that any more. Another nice feature is after your first year, your previous year data is saved and compared to the current year.
If I had a business or farm, a much more complex return, I'd hire a CPA. After working for Block, I would never recommend them or any other chain tax prep firm. Their training for preparers is minimal at best.