Porn preview sites aren't known for their usability. You're familiar with the template, I'm sure. The standard design looks like someone spilled a box of dirty photos across a black laminate floor and then vandalized the result with several colors of primary paint. In all caps. With lots of misspellings and exclamation points!!!

It's bad enough when you can see it. But what if you have a visual impairment? Your screen-reader software would probably spit out a few choice words and crash out of sheer spite.

Porn for the Blind, a nonprofit organization based in Cambridge, Mass., was established for the sole purpose of making the millions of free porn clips available online accessible to people with visual impairments.

Given the abundance of audio erotica, pornographic podcasts and adult online radio, you might think that Porn for the Blind is at best unnecessary, or at worst, a hoax.

Yet there's something hot about the absolute amateur quality of the submissions, just like a homemade snapshot capturing real sexual energy can have more impact than a studio photograph of a professional model.

"We imagine that visually impaired people benefit from this service in many of the same ways that non-visually impaired people benefit from the raw hard-core pornography that's being described," says the site's co-founder, who asked to be identified simply as Elmer.

The method? Volunteer audiodescribers watch porn preview videos and describe the content as it unfolds, using the site's recording software to capture the audio and post it to the home page.

At press time, the collection had about 14 descriptions – two of which I recorded myself. Not a huge showing for a site that launched two years ago. But sometime around April 1 (I know, I know), bloggers discovered the service. In three days, the site streamed more than 40 GB of audio descriptions to more than 50,000 visitors, says Elmer.

The website itself is simple. It has no images, no video and no ads, just text on a white background. A sighted person accustomed to the visual assault of most websites could easily pass it by. The homepage presents a welcome message and links to audio descriptions with titles like "Cum Overload." A second page contains an embedded audio recorder and directions for contributing a description, along with a list of sites users would like to hear described.

"Porn for the Blind is a distributed, community-generated accessibility project, and it is an interactive experience," Elmer says. "Users can request a site to be described or publish their own descriptions."

It takes more skill than you'd think to record a real-time description of a 20-second porn clip. You have to watch your ums and ohs – and if the scene flat-out does it for you, you have to remember to keep talking.

In my first attempt (.mp3), I spoke too fast and wasted words on useless description. Would the colors of the pillowcases matter to a blind porn consumer? Probably not: Sighted porn users don't care about pillowcases either.

But the length and texture of the woman's hair, the lean muscles of the male bodies, the shape of breasts and buttocks – those details have meaning for everyone.

For my second clip (.mp3), I watched the video twice first, making liberal use of the pause button and taking notes. I then experimented with recording a somewhat longer description than the video, so I could add detail without having to rush. But that results in audio that's out of sync with the video – not very useful for partners watching and listening together.

Most surprising was how quickly my contributions appeared on the site. It took approximately two seconds after I submitted the description for the new MP3 to appear in the list.

How do the site's operators know whether I followed the script? Or that I didn't just talk dirty and leave a 900 number for blind users to call me for phone sex? They don't. But so far, contributors have not abused the freedom of instant publishing.

"We may implement some Craigslist-style flagging if it becomes a problem," says Elmer. "In the end, the site must be community-driven if it's going to scale."

Elmer says he has fielded requests from other organizations wanting to license the software behind the site. Not that they couldn't build their own. "All the technology we use is open source (Flex, Red5, FFmpeg) and not excessively difficult to string together," he says.

New developments will stem from user feedback, Elmer says. For example, some have expressed interest in a Firefox plug-in that could automatically play back descriptions of any pornography sample clips on a given web page.

Some Porn for the Blind listeners also wish the descriptions were "sexier or narrated by women," Elmer says. "But we've been extremely impressed with most of the