I learned of a great Open Source (can you say 'free') site for assistive technology software at Closing the Gap. The site is oatsoft.org.
There is lots of good stuff on the site including on screen keyboards, voice activation, symbol libraries, full office suites and word prediction software. It's all free, but some have upgrades to more full featured products that have a nominal fee. At least you can try it for free.
With budgets evaporating, I think this is something everyone should at least consider.