If you want to Post Free Classified Ads, there are millions of classified websites where you can post your ads.
If you search on google for Free Classified Websites, you will find a long list of free classified websites. You can publish your Ads for free within minutes.
But there are very few websites with high traffic, means with too many visitors. I you post your ads on these high traffic websites, you will get more viewers. As many viewers you get, as much response you get for your Ad.
Here i m recommending you a Free Classified Website, where posting an add is very easy, No registration is required, Just one click post.
Here i usually posts my business ads and i get very good response for my every post. http://www.newlinkinfo.com is more than 10 years old website and is very much similar in traffic like olx, quikr and locanto.