Description taken directly from site"…provide teachers and students access to virtual manipulatives that directly support our district's math and technology curricula. In 2002, the BPS Office of Instructional Technology and Secondary Math Department began working with the Education Development Center, Inc. (EDC) to align technology to our math curriculum and to provide professional development to our teachers and district staff."
This is the website that David Davis from Florida shared at Closing the Gap. It has a ton of stuff for math. Somewhere there is a on screen protractor.
I have recommended this site before. In the past it provided a comprehensive comparison of math and reading programs. Now the site has been updated to include new programs, new ways of examining features and now includes writing and AT tools.
Website for the high incidence accessible technology team at the Montgomery County School District in MD. Offers links to sites on a variety of tech ideas for literacy, math, science, and social studies. Links deal with assistive tech for students with high incident disabilities.