NFB posted this video, which is jawsome and anyone who builds forms should watch it.
GMail signup with JAWS
They've turned JAWS way way way down slow so everyone should be able to hear it.
Audio CAPTCHAs are the devil. Why not non-distorted sounds of common things and ask people what they are? (Similar to the multiple cats/dogs images where you are asked how many cats or dogs... meaning you're expected to be able to tell the difference visually between a cat and a dog. Something many robots can't do).
The lack of a list of errors above the form is an easy thing for any dev to fix. You can even have them be links that go directly to the input in question.
You can also add aria-describedby attributes to the errors you have that are directly above the bad input, though I get mixed results between JAWS, NVDA (who seems to rock at forms) and Orca.
(here's a great intro/description by Marco Zehe: