All Landsat 7 ETM+ scenes held in the USGS EROS archive are now available at no charge. Newly acquired Landsat 7 ETM+ SLC-off images with less than 20 percent cloud cover are automatically processed and made available for immediate download, while all remaining Landsat 7 ETM+ scenes can be processed upon request. Once the requested scenes are processed, an email notification is sent to the customer with instructions for downloading. These scenes will then become accessible to all users.

Landsat 7 ETM+ data can be searched, downloaded, or requested from EarthExplorer orGlovis.
+ More about product processing parameters
Source: USGS EROS