We use a combination of a CSS-hidden field and a block list of known spammer
IP addresses on all of our public web forms.  This combo has reduced our
spam load by some 95% since instituted (we used to average several hundred
spam submissions a week).  The block list does have to be maintained by
regular review of our submission logs but, since the majority of spam
hitting our forms is robot-generated, I only spend about 10 minutes every
morning reviewing the logs and only find myself adding new IPs to the block
list 4-5 times a week.  I did test the hidden field in JAWS with no
problems, but be advised that some mobile devices (in particular, some older
Blackberry devices) will display the hidden form field.  I circumvented that
issue by adding an exception for mobile submissions, as I've yet to
encounter any spam originating from mobile devices.
--
Mark Vega
University of California, Irvine Libraries