I have used TaxAct online for the past 2-3 years with no problems, and no compromised info, no later spam email, etc. Before I became a SAHM, I was a tax accountant full time, and I have found this to be a trustworthy product. As I recall, they ask you a couple times if you want to upgrade to the deluxe addition to get advice on certain things. For the average taxpayer, this simply isn't necessary, so just click no. I filed electronically through them and got my refunds quickly.
Some other options:
If you make less than $54,000 a year, you can file for free via "free file" on the IRS website. Here's the direct link http://www.irs.gov/efile/article/0,,id=118986,00.html. If your Adjusted gross income is over $54,000 a year, they also have low cost e-file programs offered through a variety of vendors (most $10 or less) http://www.irs.gov/efile/lists/0,,id=101223,00.html
If you live in Illinois, you can efile for free right off their website: http://www.revenue.state.il.us/
Other states may have similar options.