How do craigslist posting services work? My only hesitation is giving out my account and password, but I guess there is no way around this, they need the account information? I'm posting in the writing category under "gigs" which needs an account.
They use software which you can purchase and use instead - which will cost less in the long run if you are going to keep posting. However the captcha can no longer be bypassed and therefore must be outsourced (good software will handle your captcha outsourcing for you).
Craigslist is the one online classified where are are assured to get good quality traffic. It has over 45 million users every month. I have made hundreds of dollars with Craigslist. You will want to take care in not spamming, or posting to too many places at once. I have had really great successes with it. Carmen
Most craigslist ad posting companies will have the accounts already so you will just need to provide information about the ad you want posted. Take a look at http://www.verifiedcraigslistaccounts.com/