NVDA 

NVDA is intended to bridge the gap between sighted people and those who have problems to read from the computer screen. The program uses speech synthesis to provide blind and other types of visually impaired people with an audio-based interface, parallel to the traditional graphical user interface.

The program is easy to install and operate. However, its users might need the help of another person during at least the first steps of configuring the tool. In this respect, it is remarkable that you can create various configuration profiles to suit different usage scenarios. Luckily, the program can be set to run automatically at startup without user intervention. Likewise, you can pick the desired keyboard layout, if you are using a desktop computer or a laptop, for instance. Not only that, the software can be installed to a portable memory device, which allows users to run it from any machine, such as those in public libraries.

It is excellent that the tool supports more than 20 languages. However, it seems to me that its default speech synthesis engine does not produce the best results. Instead, you can download additional voices, which, unfortunately, has a cost. The program supports working with Braille characters as an additional source of input for the users. Good news is that its features can be easily expanded by downloading and installing add-ons.

In general, I would say it is a blessing that such a program is accessible free of charge. It certainly saves visually impaired people a lot of money, which should otherwise be spent on commercial software. It seems logical, though, that the developers appreciate any donations that can keep the project alive.