Does ODF support people with disabilities?

Yes. OpenDocument has all the features required for full accessibility support.

Accessibility features are provided by applications, not formats. What formats do is provide a means to encode accessibility information. But it is up to the application to use this information to provide accessibility features.

For example, many visually impaired users require a speech synthesizer to read documents. The document format must allow all images to have an "alternate text" that the speech synthesizer can read. OpenDocument supports this:

<draw:frame draw:style-name="fr1" 
  draw:name="graphics1" text:anchor-type="paragraph" 
  svg:width="8.835cm" svg:height="4.041cm">
  <draw:image 
    xlink:href="Pictures/190B791AAB.jpg" 
    xlink:show="embed" xlink:actuate="onLoad"/>
  <svg:desc>
    Photograph of the Rocky mountains
  </svg:desc>
</draw:frame>

But it is up to the application to support that feature. It is also up to the makers of speech synthesizers to support an application that uses these features.

Current work

The OASIS OpenDocument technical committee has an Accessibility subcommittee that is constantly auditing the specification to ensure that the specification addresses the needs of people with disabilities.

Likewise, OpenDocument supporting applications like OpenOffice.org and KOffice are constantly working to improve their accessibility features.

14 Dec 2006
IBM Helps Disabled Users Get More From Assistive Technology, on More Computer Platforms
"IBM announced that it had developed software interfaces that will make it easier for assistive technologies to provide those with disabilities access to advanced features in software programs -- such as ... desktop applications based on the OpenDocument Format."

03 Sep 2006
Announcing Orca v1.0.0
Orca is a free, open source, flexible, and extensible screen reader that provides access to the graphical desktop via user-customizable combinations of speech, braille, and/or magnification. Orca has been been developed by the Sun Microsystems, Inc., Accessibility Program Office. The focus for Orca v1.0.0 has been to provide usable access to keyoffice productivity applications, including the following: GNOME desktop, yelp, gedit, gnome-terminal, evolution, gaim, OpenOffice Writer & Calc, and StarOffice Writer & Calc.
ORCA Live!

24 Aug 2006
IBM Accessibility ODF Coding Challenge 2006
"Want to change the world? Start with the code... an opportunity to showcase your own unique brand of creative genius. Get some excellent experience. Score some cool prizes. And maybe use what interests you most - technology - to improve the IT experience of a wide range of users..." For undergraduate students.

29 July 2006
Openness, ODF and Accessibility
"On July 27, the OASIS announced that the first draft update of ODF (version 1.1) has been posted for public comment. This draft is more than usually significant, since it seeks to make it easier for those that implement ODF to make their applications more accessible to those with disabilities."