For all the talk of how expensive screen readers are, there's one that developers have loved using on Windows, first and foremost because it's free: NVDA. http://www.nvaccess.org/
Unlike programs like ChromeVox and Fangs and FireVox, NVDA is a "real" screen reader used by real users.. but it's also become standard in testing for accessibility of web pages, PDFs, and desktop programs. And its developers (pretty much just 2 guys, though there are some volunteers helping out here and there) need help.
The Sydney Morning Herald did a story on them:
(Adobe is still a yearly funder, the article wasn't clear there).
They need help. Mostly funding. They have a donate page: http://www.nvaccess.org/wiki/Donate but people also volunteer things like testing, sending in bug reports, etc. too.
Mike Paciello also ran an article about the importance NVDA has gained recently: http://www.paciellogroup.com/blog/2012/03/is-nvda-strictly-a-web-accessibility-screen-reader/
In the comments, it's mentioned that JAWS costs $4000 in Iceland, and they had difficulty getting an Icelandic translation. With open-source NVDA, they could just take care of that themselves. And users who rely on screen readers but can't cough up huge amounts of money, or need local community resource centers to have screen readers so people can come and learn to use computers and computer programs, need programs like NVDA.
A recent blog post on PDF testing included NVDA: http://accessibilitychatter.com/?p=18
And Jason Kiss lists NVDA in his web page tests: http://www.accessibleculture.org/articles/2012/03/screen-readers-and-details-summary/
Also if you want to bring a screen reader with you, with programs like JAWS you need admin access to the Windows machine at least once to install the video intercept. With NVDA, you can just have the whole program on a USB stick and use it wherever you need it (Windows-only of course).
If you like the idea of keeping free open-source software like NVDA around and maintained for people who simply cannot afford the commercial programs, please consider donating!