To help both non-English speakers and people who can't type very well, I've created a GreaseMonkey script which checks your response to the FancyCaptcha challenges seen on Wikimedia and elsewhere.
http://userscripts.org/scripts/show/96233
The script is not specific to GreaseMonkey and could easily be provided in some other way, such as a gadget or site JS.
The check is done as you type, and a tick icon is shown instantly if the response you have given matches a pair of words in the dictionary. This helps you to spot typos before you press "submit".
Restrictions in FancyCaptcha mean that the dictionary only needs to have about 8500 words, so it's easily embedded in the script.
My original idea was to search for near matches and to provide an autocomplete drop-down, but the necessary UI code for that seemed a bit too complicated for a quick weekend project. Maybe later.
-- Tim Starling