If you are getting the 'You are posting too rapidly. Craig can't type them in this fast. Please try again in a little while.' message while trying to post to Craigslist.org, it's because you're trying to post to many ads too quickly.
There are many Craigslist spammers and spam bots out there that try to post instantly, so Craigslist has to set a timer cookie for each poster to ease the burden on bandwidth and server resources.
You are posting too rapidly Solution
Click the 'Edit' Again' button, wait 3 minutes then click the 'Continue' button to post the add again.