Yes, *selected* Landsat is free. To access, go to earthexplorer.usgs.gov, then select any of the 3 orthorectified offerings: ETM +, ETM + pansharpened, or TM. Specify additional search criteria as appropriate. If the database finds any matches, it provides a download link on the results page.
I hope this is helpful.
Joseph Kerski - Geographer - USGS