Google Docs and Sheets have built-in text-to-speech functionality. Although it may be less accurate than other programs, it is embedded in the applications themselves and easy to use.
Google Slides and Sites likewise have built-in auto-captioning tools that work most of the time. This might be more useful for professors, as they work to make their lectures accessible.
These applications are part of Boxer Apps and can be found at the Boxer Apps Dashboard.