One of the reasons that many designers have so much trouble creating accessible web pages is because they can't even imagine what it's like to try and use the internet with limited or no vision. Designers who are serious about accessibility try to make up for this lack by using screen readers such as JAWS for help in testing their pages. Another tool that visually impaired people use to access websites is WebAnywhere. This is a tool that reads web pages aloud from any computer. By using that tool yourself on your own web pages you can better understand how to make your pages more accessible. Another good thing to read is Andrew Leibs’ article How Blind People Access Computers. This article explains how you can improve your pages so that they work better for the visually impaired. And that makes your site better for everyone.

I don’t use Jaws, because the license explicitly forbids to use it for testing sites, unless you pay the (very high) full price for the professional license.
Jaws has a nice try-out feature: you can use it for 40 minutes for free. If you want to use it longer, you have to restart your computer. That’s usually long enough to test a site. But as said: Jaws forbids to use this for testing sites. You have to buy their professional license. You can read about that here: http://clearhelper.wordpress.com/2010/03/16/stop-using-jaws-for-web-accessibility-testing/ (and in more places).
I’ve been using NVDA for some time now for testing sites. NVDA is at least as good as Jaws, but it’s free and open source.
Thanks for letting us know about that gotcha with JAWS. When I’ve used it it’s been paid for by the company, so I never really paid attention to the licensing.